If there is, that would clarify the situation.
But it's an important point that the shooter was an ex-cop who probably believed himself to be playing a quasi-police role in his neighbourhood.
His neighbours probably knew his background and deferred to it.
On the other hand, his powers as an ex-policeman are not the same as he once had.
Messages and emails will be the best evidence available. But it's definitely the usual second amendment nightmare we keep revisiting. The second amendment is 90% of the problem.