So the whole "perfect crime" I don't get.
They tracked a lot of his movement via street cameras by now, so while he did a really good job, he's also not infallible. He left behind his backpack with a jacket and the monopoply money which is hilarious but incredibly risky. They did also pull some trash and a phone he may have dropped right?
there's also a world where maybe he's either a rich kid with a sense of self-righteousness and just wants to get his manifesto out, OR where he's a bumbling idiot, or mentally unstable even, which would lead to irrationable moves like keeping the suppressor and gun on him.
There are so many variables to this, it's silly to immediately put on the tinfoil hat.

See what develops, see the facts present themselves as this goes on, and draw a logical conclusion once there's enough.