Welcome Joshua. I’m familiar with the attack the messenger strategy, which is a common way Trump deals with anyone who doesn’t agree with him. In that way, he can avoid the issue raised.
Obama was POTUS when some of these atrcocities occured, but he was’t in control of the outcome of gun-related legislation. You didn’t tell me where you stand on the specific issue of high-powered automatic weapons and high-capacity-magazines, but unless you tell me differently, I’m guessing you’re good with the status quo. If you really have an interest in which leaders are doing what, may I suggest you take a closer look at what Obama attempted to accomplish verus what Trump has avoided addressing.