And this is why I say things like “first 48 hour rule is in effect”, and to assume most of what we hear is bullshit.
Even if it were an undocumented illegal alien, odds are he had a wallet, or a phone, or a car nearby that he used to get there, or all of the above. He’s probably not some random rifle-hobo who lives in that building’s dumpster; he came from somewhere and had means to get there, and unless he deliberately sanitized and took transport that’s difficult to attribute, likely there’s ample easy evidence towards ID. I wouldn’t think that likely; he had to know this was a one way trip. Shit, just from photos of the body on the roof it looks like the internet has already managed to identify the specific shirt he was wearing (most likely a Demolitia shirt, potentially a Grunt Style ‘SFMF’ tee).
Law enforcement will likely have an easy time getting a preliminary ID, and probably not a super hard one confirming it.