Several investigations are now underway into the shooting at a Trump rally in western Pennsylvania that left former President Trump wounded, a bystander dead, two more people badly hurt, and the suspected shooter killed by Secret Service snipers.  

ABC News chief investigative reporter Josh Margolin on Sunday received reports that authorities outside the security perimeter on Saturday were alerted that a man was acting suspiciously. Local and state police, responsible for security outside that perimeter, began to search for a potential suspect, multiple sources briefed on the probe tell ABC News. 

Within minutes, law enforcement spotted the suspected gunman on the roof.  It is unclear, however, whether this information was passed along to the Secret Service responsible for the security of the former president and the crowd inside the security zone. A police officer saw the suspect on a rooftop and attempted to make it to the roof to engage the shooter. That officer was threatened when the gunman pointed his rifle at the cop. That effort did not succeed as, moments later, shots rang out, targeting Trump.  ABC News chief invesitgative reporter Josh Margolin