No, I am not certain, as I (like you) await more facts. However, from the history of other such massacres, and considering that this shooter is said to have a history of mental problems, it would seem extremely likely. Clearly, this fellow was bent on seeking suicide by cop.
[I have wondered how many of these mass shootings were caused by people under psychoactive drugs.]
In most of these, drug-induced violence and suicide have been prominent, as we have seen by many past lengthy FR discussions. But the medical records of many of these have not become a part of the public record. One suspects the reason is because of tacit suppression by the drug companies.
Or, to push the gun control agenda of the Left, politicians, and MSM. It isn't a good idea to advertise that this crazy killer was the best customer of “Dr. Feel Good” or local dope supplier. Notice that no mention is ever made of the perp’s previous drug use or abuse.