The gun was reassurance. Sherlock wasn't a murderer. Not in the sense that he went out intent on ending the lives of other humans anyway.
Sherlock honestly couldn't believe the man a few steps in front of him had the nerve to call himself an assassin. The man has flicking through social networking sites on his top of the range phone oblivious to the man who had been following him for almost 7 minutes. Sherlock silently rolled his eyes. The street was empty now. Sherlock took this moment to advance.
"Mr. Simons?" he asked politely. The man turned around
"No" his eyes widened "But you're-"
"The late Sherlock Holmes. Yes"
The assassin reached under his jacket but Sherlock was quicker
"Hands where I can see them" Sherlock commanded his gun aimed at Simons' head. The man paused before obeying.
"How did you do it?" Simons hissed
"That is none of your concern" Sherlock told him before stepping forward and whacking the man with the butt of the gun, knocking the assassin out cold. Sherlock pulled a pair of handcuffs from one pocket of his coat attaching the man to a lamp post, and planting papers in Simons top pocket that would insure his immediate arrest on being found.
Sherlock straightened up. Another job done. His next target was a Thomas Blakley who had recently moved to London. Too close to DI Lestrade for Sherlock's liking. It looked like Sherlock would be returning to London, even if only briefly.

DI Lestrade was stood in front of a desk. Papers spread out into front him. He reached back to itch the back of his neck a groan of annoyance escaping his lips. There was nothing. The victims all suffered the same cause of death, cyanide poisoning. Approximately an hour after death each had received a bullet through the head and been left for the police.
It was days like this he needed a consulting Detective.
Both Sally and Anderson had offered their thoughts on the case but both knew what Lestrade was thinking. They had eventually retreated from the room. Leaving Lestrade with the case.
He glanced at his watch. 5:35pm. He could go home now. He grabbed his coat draping it over his arm. With weather like this he didn't know why he'd brought it with him in the first place. He reached his home quickly he struggled with his coat to find the keys and slid them into the lock of his flat. That when he saw it. Pinned to his door. The handwriting was large and in capitals.
THEY ALL HAD THE SAME CLEANER. ISN'T IT OBVIOUS?
What was that supposed to mean?

Lestrade was in his office rooting through the papers and evidence. Again.
"Greg?" Sally stood in the door way. He had taken a disliking towards her since Sherlock's…absence.
"What?" his tone wasn't to harsh
"Just some more information. We already knew they were all neighbours, but turns out they used the same laundrette and cleaner" she handed some papers his eyes scanned them quickly, then he remembered the scrap of paper. He searched his trouser pockets and fished it out.
THEY ALL HAD THE SAME CLEANER. ISN'T IT OBVIOUS?
Lestrade read 6 times, It seemed like such a Sherlock thing didn't it. He supressed a small laugh
"Donovan I want to question the cleaner"
"The cleaner?"
"Yes. The cleaner. Can you have it organised?"
"Ok…I can get it sorted within the hour" Sally left the room. Greg looked down at the note again. Shaking his head slightly, he scrunched it up in his hand and was about to through it in the bin but changed his mind. He straightened it out and placed it in one of his desk drawers. He wasn't sure why.

John had rented a new flat for 6 months after Sherlock's passing. It was on London's outskirts but he couldn't really afford it without a good job. Apparently Sherlock had paid a 18 month advance on Baker Street.
At first John had an aversion to 221b but now, with money running low and him feeling lonely he had moved back in. This had pleased Mrs Hudson greatly she was constantly making him mugs of tea and fussing over him.
John had packed all of Sherlock's belongings in boxes and moved them into Sherlock's old room. He couldn't bring himself to bin them but he couldn't look at them everyday so it seemed like a good compromise.

John had had a job interview today. He was going to be an A&E doctor at the Royal Hope hospital, it offered a lot more variety than the small surgery he'd worked at with Sarah. But she was gone now and so was that John. He had changed after the war and he had changed after Sherlock's death.
His new job started next month. That gave him about 27 days of lounging around all day. In the corner of his eye he noticed a small pile of post. Mrs Hudson must've brought it up. He stood up and headed towards it, flicking through it;
Bill
Bill
Spam
More Spam
The last letter caught his attention though. He placed the others down. The address was hand written and the envelope made of thick expensive paper with a creamy tinge. He flipped it over and opened it, pulling out a letter, also hand written on the same paper.

Dear Dr. John Watson,
I am writing to inform you that you have been invited to this years Hunger Games.

John gave a disgusted snort.
"What the hell?" he muttered throwing the letter over his shoulder. The Hunger Games, it all seemed so long ago now. They'd been cancelled now. To many counter movements. John walked away from the letter deciding he needed another cup of tea.

After a half an hour it was concluded that the cleaner was the killer. His team had been ecstatic, a case hadn't been solved this quickly since Sherlock. But Lestrade kept going back to the note. Where had it come from. Was it a prank? Someone pretending to be like Sherlock? Or just a witness to scared to come to the police themselves?
Either way it was case closed.
With no more cases waiting Lestrade headed home at 5:00pm for once. When he reached his door there was another note.
TOOK YOU LONG ENOUGH
Lestrade shoved it in his pocket and went inside.
So he had a stalker now then?