I don't "know" if he is psychotic or not but a person who had drinks with him at a bar just two days before the shooting said he appeared normal at that time and there was no apparent psych problem or distress.

The shooter spent a great deal of time buying guns and ammo and setting up trip wires and explosives in his apartment. I don't know if he could have done this over that long period of time if he were having a psychotic break with reality.