Sure, Trump bares some responsibility, not ALL and not NONE, but some responsibility that would be difficult to quantify. Words do matter.
I think Trump does bare 100% responsibility for rolling back Obama-era regulation that would add anyone receiving Social Security checks for mental illnesses to be added to the national background check database.
Who thinks it's a good idea to have folks with enough mental illness to collect disability checks should be allowed easy access to guns? Not me!