That's a good bet, but we don't know. Remember right after the shooting on Blenheim we were told the victim was armed and shot back and it turned out he wasn't armed and the scenario was not what we'd been led to believe? I just don't want to jump to conclusions even if they seem reasonable.
Unless I missed some fast-breaking news, I don't think we know that this gun was dumped by a felon. It is very unsettling, to be sure, because our minds race to thoughts of what could have happened if a child had picked it up. But it could have been dropped by someone who owned it legally. We just don't know at this point.