 ABC News has learned the shooter's father legally purchased the AR-15 style weapon used in the shooting. John Cohen, a former undersecretary at the Department of Homeland Security and an ABC News contributor, says of the current climate. There are a growing number of people in this country who believe that violence is an appropriate way to express their ideological or political views or to express their disagreement with others. And the Republican National Convention will go forward as planned beginning Monday. President Biden said Saturday at the White House.