What to KnowFormer President Donald Trump was injured Saturday in an assassination attempt at a campaign rally in Butler, Pennsylvania.The shooting is being investigated by the FBI as an act of domestic terrorism. The FBI believes that the suspect, a 20-year-old from Pennsylvania who was shot dead by Secret Service, acted alone.One spectator, 50-year-old father and former firefighter Corey Comperatore, was killed after shielding his family from the gunfire at the rally. Two others who were injured are now in stable condition, officials said Sunday. Authorities were working on Sunday to understand how a gunman armed with an AR-style rifle was able to get close enough to shoot and injure former President Donald Trump at his rally in Butler, Pennsylvania on Saturday. The brazen act of political violence shocked the nation and the world, with foreign leaders condemning the attack with messages of support and wishes for a successful recovery for Trump pouring in from leaders around the world. President Joe Biden, who spoke with Trump earlier in the day, was set to deliver a pre-time address on Sunday.