AN: this turned out a lot more poetic than I'd hoped for, but oh well.
Gabriel was a man of the arts first and foremost. He made it a point to show the emotions though each piece that he felt at the time they were created. And if his media just so happened to be human corpses, who could really fault the brushstroke of genius? Well, obviously the law enforcement, which was why he had to leave his masterpieces signed under the pseudonym "The Candy Killer". Though his title was dubbed by the media, he still found he rather enjoyed the name.
It was a shame he didn't get paid for his beautiful work, but then not everyone had as good of taste as he did to see it his way. He had started his art when he was young, though admittedly it was different media then, but he'd had no one to impress, no audience; mother always away with another and father drinking away his sorrows and taking his aggression out on his children. Gabriel had plenty of scars covering him to prove it. They were ugly and marred his skin in the worst of ways until he could barely look in the mirror half the time. That was until he'd learned of the joy found in his mother's make-up kit.
He stared at it for ages before the first time he put it on, trying to remember exactly how she'd done it. How she'd cover up all the imperfections that humans seemed to have and be flawlessly perfect; mediating between his older brothers and taking care of Castiel while still keeping enough time out for him. Mother had been like him. Special, she called it. That's why father hated him the most when she left. For his first time working with the magical array of colors, he'd say he did rather well. He wanted to be an artist and show people how beautiful his thoughts were and how were they to do that if they saw his damaged outside?
There was one though. One little boy about Cas's age who smiled at him because he wanted to, not like Cas. Cas had to because Gabriel stood in for mother and took care of him. He made sure his angel of a brother had everything he needed to be happy, even if it was at the expense of himself. Cas was good and smart and not at all broken like him. Cas would go places and not have to worry about a dinky little town he grew up in ever again. He could feel it. But back to the boy. He was thin and lanky and smart. He would be like Cas. Too bright of a light to let the flame burn some place so dull. He had old eyes that saw right though him, with one glance and Gabriel honestly couldn't tell if he liked it or not.
It was years later before he looked in the little boy's eyes again and this time he was looking up into those eyes that still saw right though him; saw completely past his painted mask of careful lines and shading and still stood up to the beast there. Gabriel never meant to fall for him, but this boy, this Sam was just another thing in the long list hidden under his bed labeled 'things monsters can't have', because if he wasn't a monster then why did everyone think so?
When Sam, beautiful amazing wonderful Sam, was stressing out that he might like an older guy, Gabriel was the first person he told. Sam thought he was disgusting, thought himself repulsive and wrong and was in such a dark place that Gabriel wasn't sure he'd ever see that light in knowing eyes again. And that's when he'd done something monumentally stupid: he'd looked Sam in the eyes with confidence he didn't have and kissed him square on the mouth. It was so good while it lasted, Sam making such beautiful noises and pushing back with the same force until he ripped himself back and wiped his mouth with a glare. Honestly Gabriel expected to be hit with a look like that. But it was worse, so much worse, Sam, amazing perfect beautiful Sam with his eyes that knew of deceit and smile that told of secrets, left. That beautiful light left and never came near him again.
Castiel got a scholarship to study abroad in Italy for his wonderful mastery of Latin. Needless to say he was on the first flight over. Sam came out to his family the day he left for Stanford. His father threatened to kill him and became The Candy Killer's first victim. Sam only came back for the funeral and wouldn't say a word to anyone. Dean took some time off in Europe soon after.
And Gabriel? He had nothing to do. He was useless and wouldn't amount to anything like dad had said, but he was good at one thing: Keeping his light safe. So that's what he did. He hitched hiked to California with jokes and good humor. He never hurt anyone who drove him. They took care of him when he told them about the love of his life at Stanford, waiting to see him again. Though it wasn't exactly true, it fit well enough.
So he lived off campus and watched amazingly perfect Sam fall in love with another because no matter what, Sam was always his to protect and make happy from afar. If this Jess could do that up close, who was he to argue? But then Jess hurt his Sam. Now Sam didn't know about it then, but he did. So The Candy Killer left another victim in his wake.
Then came Ruby and Azazel and they tried to take what was his, tried to use him so Gabriel smote them with all the power of the angel for which he was named and two more victims were added on to the body count. It was a few months later when Sam saw him in California for the first time; He offered to buy drinks and catch up, Gabriel accepted and saw that beautiful perfect smile aimed at him for the first time in years. He nearly melted on the spot.
Some months later they'd moved in together and Gabriel was on top of the world. That was when Sam noticed the make-up. He asked him to take it off in that loving gentle perfect way of his that meant anyone with a heart had to listen and the older man caved.
Sam kissed every scar and made him tell every story behind them and most of all, he told Gabriel that he'd love him no matter what. That he didn't have to change himself. That was when he let those three little words with so much power slip and Sam smiled so wide he was sure his face would break.
But then Kali had to ruin it by piecing it all together. All the little clues in his art, the little things that pointed back to him, like Jess's teeth being replaced with candy corn and tongue with saltwater taffy or Ruby having her shoddy make-up job redone in Fun-Dip and Pixi-Stix or Azael even, lemon heads in place of yellow-brown eyes and chocolate shoved down his throat until he couldn't breath. Kali, his dear precious friend Kali, knew far too much. She'd puzzled it all out. She didn't even know about John then, but she was smart. Too smart. He told her that too when she'd tried to scream. He wasn't a fan of the screaming. Hated it really. It reminded him of his parents fighting.
He was still covered in blood when Sam came home. Perfect Sam just laughed his melodious laugh and asked if he had a hard day at the studio. It was so amazing and understanding of him, that Gabriel just nodded with an affirmative and kissed him, saying that he'd go clean himself up real quick and he'd make dinner for them.
Then there was Dick Roman in the apartment next to Kali's who said he'd heard everything. He threatened to tell the police but then Sam wouldn't be able to see his surprise and he would get mad because Gabriel wouldn't be able to make it to their anniversary and give him that kicked puppy look that made him feel worse than if he'd actually kicked a puppy (He had a big aversion to hurting animals anyway, so that says something). Really by now, people should have known that Gabriel would do anything to make his light in such a dreary world smile that perfect smile and his latest work of art would do just that. He was sure of it.
So Dick went down, trying to fight unsurprisingly but Gabriel being smaller and faster, stabbed him in the neck with a syringe full of nerve paralyzer and smirked as he fell to the ground. It seemed as though this project was gonna be a big one.
Three days later is was their anniversary and Gabriel had nearly forgotten in his endeavor to make sure Sam's gift was absolute perfect so he was running a bit late with blood streaks across his face and on his hands. He would have explained to Sam ], but it was going to be the perfect surprise gift and Sam would love it.
His amazing Sam had cooked them dinner and everything was nearly set up by the time he got there, it seemed as though Sam was running a little late too. They smiled and talked and just basked in each other's presence when Gabriel took his hand and said he want to show him something.
They stood outside Kali's apartment as Gabriel clicked the lock open and took up Sam's hand dried blood flaking off of his palm. He lead Sam to the bedroom where his art work was set up and swung the door open pulling him inside.
Sam looked so shocked and Gabriel bet that he surprised him big time with this perfect gift. It was sort of a compilation of all of the killings. Pictures of the crime scenes tacked on the walls hanging over the bodies in the order that they'd been taken care of. When Sam hadn't said anything for some time, Gabriel pouted. He put so much hard work into it to make it special. "Sam-a-lamb," he called, "Don't you like it?"
Sam snapped back into reality and yanked his hand away like it burned him, "Gabriel, what the fuck is this?" He looked so scared that Gabriel just had to reach out and calm him down. He moved a hand to his cheek and smiled, "It's your anniversary gift, kiddo. I killed them all for you."