No ID on his person, but they knew his age before his name. Did they count the rings on his skull?
They knew who he was before he went up on the roof. I am sure he wasn’t “hired’ to do the job but some “retired” FBI man talked to him maybe a couple of months or a couple of weeks ago, getting from his NSA/DHS profile that he was unstable with a repressed tendency to violence, suggested some things to him like how to make himself famous, maybe. Those “retired” or not so retired FBI/CIA fellows had contact with many of the school shooters over time prior to their actions.