It explicitly said in the article that he pulled out a gun. He shouldn't have been swatted, obviously. That said, if you pull out a gun when police are responding to what they believe is an active shooter, the chances of you being shot are extremely high.
Additionally consider what would have happened if this had been an active shooting and they simply disregarded the phone call.
Additionally consider what would have happened if this had been an active shooting and they simply disregarded the phone call.