Man Armed With 4 Guns and Several Knives Tried to Attack a Comic Convention in Phoenix

According to KPNX News, Mathew Sterling tried to enter the Phoenix Convention Center, where Phoenix Comicon was being held, with three armed handguns, a shotgun, and several knives and swords. Police were informed that Sterling had been posting on Facebook that he was looking to kill their officers on site, wreak havoc, and assassinate celebrity presenters. Of course this threat occurred within a week of the deadly soft target attack in Manchester, England. Should convention and event attendees in the United States be concerned that they might be next?