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.