Several Days Later

A knock sounded on the door.
"It's just me, Officer Hopps," Judy stated. "I've brought a friend of mine to help me talk to you, can we come in?"
"That depends," Kai responded. "What about the other fourteen hiding just around the corner?"
Judy paused.
"What?" she asked.
"Don't play dumb, my scope has thermal resolution, I can see them through the walls. I would presume you brought with you a SWAT team, seeing that they have a hydraulic battering ram and several tranquilizer rifles. But, by all means: if it's only you two, come in."

Nick and Judy entered, and closed the door after themselves. As they looked around, they noticed it was only the three of them in the office; perhaps the hostage was hidden behind the desk, but she couldn't check yet.
"Lock the door," Kai demanded. They turned the door lock. "Excellent, now we can get our discussion under way."
"So, what are your demands?" Nick asked smoothly.
"You don't have anything that I want."
"Oh, come on. Everyone wants something, and we have everything."
"Do you have a time machine?"
"Well… no, but-"
"Then you don't have everything."
"Perhaps you want a way out? An escape vehicle?"
"Please, if I leave through that door I'd have to go through fourteen wolves with guns, and that seems counterproductive. No, I'm content sitting here for the time being."
He suddenly sniffed at the air, and began to laugh.
"What's so funny?"
"Isn't that cute? You two are mates!"
"W—what?" Judy asked suddenly.
"I can smell him on you, rabbit."
"We are in the same room, you know."
"No. Back when I went fox-hunting, I learned the smell of their pheromones. This is that smell."
She and Nick both looked in opposite directions.

"What are you playing at?" Judy asked after an uncomfortable silence.
"Oh, I'm stalling, plain and simple."
"What? Why would you do that, stalling puts you at the disadvantage; even as we speak, we're getting our officers into position."
"Well, I guarantee that they aren't getting into the correct positions."
"Why's that?"
The killer stared out the window.
"For starters, your snipers are in painfully obvious spots, none of which have a good vantage point on this room." He returned his gaze to them. "Second, the SWAT team outside isn't in a proper breach orientation. They'd trip over themselves trying to get in. In addition-"
"So, what are you even doing in here? Surely you didn't come just to stall us out?"
"No, of course not. I came to download every file in your system." Kai waved a small computer chip tantalizingly. "But, now that that's done and done, I'd best get going. The only question is how to minimize the casualties..."
"What, you grew a conscience?"
He laughed.
"I never cared much for senseless killing; I only kill in necessity. It's a waste of time to do anything else."
"What about the hostage, then?"
"What hostage?"
"...What? What's behind the desk?"
"Is there something behind the desk?"

They stared at each other for a moment, before Nick immediately grabbed at his radio.
"Chief, he doesn't have a-"
Kai whipped a dart gun out from under his coat and shot Nick in the ribs; immediately, the fox doubled over and dropped the radio. In response, Judy drew her tranquilizer and shot every dart in the clip in rapid succession; every dart save for one deflected off of his vest; the last one embedded in his neck, which he tore out and crushed in his palm.
"I'm sorry, but I can't let you relay any information." He quickly leaped to the window, broke it open, and perched in the frame, ready to jump to the street below.

Judy sat by Nick's side; he was foaming at the mouth, his form was hunched over, and he was clawing at the floorboards.
"Nick, snap out of it!"
Kai took one look back at them; he fished a syringe out of his vest, threw it on the floor next to them, and jumped out.

Several Days Prior

Kai's search for a library had taken him across the rooftops of the city's downtown area. He needed information on the city, and any information on the past would be an added benefit. However, as he leaped from rooftop to rooftop, he couldn't quite seem to find anything.

On the left, something caught his eye. 'Downtown Bibliothek'.
"Strange, why German?" he muttered. As he leaped to the next building, his lack of attention caused his foot to slip, and he began to tumble. He made a vain effort to grab the ledge, but just barely missed. He fell five stories, and somehow managed to land on his feet in a large pile of garbage cans and bags in the alley between the buildings; the resulting cacophony was the exact opposite of what he wanted. As he stood and brushed himself off, he heard windows open up above him. Eyes began staring, animals began yelling down at him. Looking up, he could barely see a ladder for the fire escape, but it was too high to reach. He desperately needed a grappling hook, or claws of some sort to climb with. He wished he was a cat, only for a moment.

Kai instead resorted to sprinting out of the alley and into the street. Thankfully, as he ran down the street towards the 'Bibliothek', he encountered no one else. When he reached the building, he peered through its glass windows: no one inside, but rows upon rows of bookshelves and books. He got lucky.

He picked the lock and entered through the door; as expected, no alarm went off. After all, why would anyone have any reason to alarm a public library? He quickly found the non-fiction section and set to work reading.

He found out many important things about the city: the dividing walls were varying climate zones; the citizens preferred to be called 'mammals', and not 'animals', the latter term being reserved as an insult for savages, or for other species that were not mammalian; projectile firearms were forbidden in the city, following the 'Animalia Massacre' fourteen years ago; two years ago, former assistant mayor Dawn Bellwether attempted a coup by poisoning predatory species with a toxin extracted from Midnicampum Holicithias, the night howler. The toxin caused uncontrollable aggression, which led to numerous maulings.

However, he could not find anything about humans. Apes, gorillas, any other primate; just not people. He could have checked the fiction section, but decided against it; after all, monsters existed in human literature, but people had never encountered them.

Suddenly, a jingling rang out at the door. Kai glanced around the corner of the bookshelf and saw that a moose was unlocking the door. He saw the clock just above the doorframe; 6 AM. He quickly adjusted the clock in his mask, and began thinking about a plan to escape; he had far overstayed, how could he have lost track of time? The moose stepped in, and Kai began to make his way to the door through cover of the bookshelves.

The door was ten feet away, but there was no feasible way to get there without being spotted. The moose was standing behind a desk, only occasionally turning away for moments at a time to get things set up. Kai timed the moose's turning pattern, and right when he turned his back, the man sprinted for the door.
"Hey! Who's there?!" the moose shouted, running to the door; however, Kai was already out and around the corner.

He had found his knowledge. Now, he had to get to the top by any means necessary. He could think of two ways to do that: the first was to ally himself with someone in a position of power. The second was fear, the easiest way to control a population. The latter was the far easier option to exploit, and didn't require any further research. How could he instill fear into the masses, however?

Several options came to mind: terrorism, mass murder, selective killing. Of all of the options, selective killing required the least death; in fact, he could cull those that he didn't want in his society. His nature dictated that he come out on top, and that disobedience was weakness. So, he could choose to kill the disobedient of society; the murderers, rapists, and criminal degenerates that ran around on the streets. All he had to do was make it seem like there was no pattern to the killings, and do it in a gruesome enough manner that mammals were afraid to go on the streets; the final part of the plan would then be to stage an intrepid heist on the police; if they couldn't take him down, who could?

Of course, then came the vigilantism problem: that plan would only give him de facto power, and he wanted the lawful, de jure control of the city. He would stop at nothing to be the lord of Zootopia. However, that would have to come later.
Fear breeds power over the fearful, and the strong will always dominate the meek. That was the master's motto, and it would hold up well; once he had authority, he could convince anyone to do anything, even give him power.

He set off out of the city, and back to his lair to being setting his plan into motion. The first thing he did was create clawed gauntlets out of gloves and nano-material, such that his little prat fall off of the building would never happen again. He threw a ballistic vest and some other reagents into the fabricator, and set it to trial and error; the beauty was that he didn't have to know the chemistry or physics behind the compositions. The machine could try and test every feasible combination and then use the strongest result.

The next thing he planned was how he would carry out his killings. He decided to maul the victims to death, for several reasons: the first was that he now had claws, which compounded into the second reason; mammals were deathly afraid of night howlers and their effects, seeing what happened with Bellwether's brief but chaotic reign of terror. He would tear his victims apart, and then leave a night howler by them; he thought the irony of such a pristine flower being used as an instrument of such a savage death would make for great media coverage, and thus a great tool of fear.

He set out to collect the flowers, before returning to his abode. Now that everything was prepared, he could begin his killings at dusk of the next day. He would wait and watch for crime, step in and kill the criminal, and escape unseen, leaving just the blue flower.

10 PM
Tundratown

Kai sat perched on a rooftop in Tundratown. He had been waiting for several hours, moving from location to location. Suddenly, he saw someone dash out of an alley.
"Help!" she shouted. "He's going to kill me!"
After her chased someone, bearing what appeared to be a knife; he was slowly but surely gaining on her. As she turned into a second alley, Kai pounced from the rooftop.

He landed just beside the assailant, who recoiled in shock and managed to slice along the length of Kai's forearm. In Kai's haste to gear up with stab-proof gear, he forgot his stab shirt; he only donned stab pants, gloves, and a vest.

Kai roared and seized the assailant, now evident to be a wolf, by the throat, and instantly broke his neck. He had hoped to be much quieter and stealthier, as well as to not be injured, but now that he made some mistakes, he would have to work quickly. He set to work with his claws, dicing up the corpse, faking a savage mauling; when he was done, it appeared scattered across the street. He then fished out a night howler from his coat pocket and gently laid it in the snow, next to the wolf, before running off.

One down, but a sloppy job. He would need to bandage up his arm and get a stab shirt before he could resume. He returned, as quickly as he could, to his bunker. First, he removed his gear and rinsed the blood from it. He discarded the old shirt, and found a new one that could withstand some abuse. He had no need for antibiotics, as his immune system was already good enough to handle anything he could throw at it, and he had no need for bandages, as the cut had already healed by the time he had reached his lair.

By the time he was ready to set out, it was already one in the morning. He made haste back into the city. He could waste no more time.