Notice that, although it says “False,” the story proves they've never caught the suspect and, if the suspect was actually the robber committing other crimes, somehow that robber forgot to get the money and phone from Seth.
So, it wasn't the robber they say it was.
So, it most definitely can be someone with a reason to only kill Seth.
I was taken aback, that you would call a fellow freeper a tool! Then I saw that his name was Tool. Lol.
They also completely discount the idea that a low level staffer could possibly stumble on something he shouldn’t have seen, and also might have the tech skills to do this.