If he regularly shot pictures of women or something sure but owning a lot of guns or buying ammo in bulk isn't really any indication of domestic violence. The son even said there wasn't a history of violence. It seems like the heavy drinking or arguments have more correlation than anything.
Media outlets often cite things like how many guns someone has to freak out people who don't know about guns. All the dude needed to fuck up was a single handgun and a single bullet. If he was drunk he shouldn't have even been carrying. And being drunk isn't really a good argument for why someone got violent.