Well, the alleged shooter was found in a locked room with no other exit, and the door was barricaded. It seems unlikely anyone else shot him. In addition, he had picked a location to shoot out from from which authorities had easy access and from which he had no escape route, and continued shooting from a static location for a long time. He had also taken so many weapons (at least 10 long arms) to the room that it can be supposed he meant to withstand a siege but certainly did not intend to escape quickly or to retreat to a strongpoint. All suggests he planned to die there one way or another.
He had been losing money heavily at gambling, he was drinking heavily and his girlfriend had left the country.
These things support a conclusion that he was at least temporarily deranged, in the absence of a clinical diagnosis.
I got all this in 5 minutes from Wikipedia.
Doesn’t seem like a live news story.