The shooting at former President Donald Trump’s rally in Pennsylvania is being investigated as an attempted assassination of the former president and presumptive Republican nominee, law enforcement officials say.

Trump’s campaign said in a statement that the former president was “fine” after the shooting in Butler, Pennsylvania. A local prosecutor said the suspected gunman and at least one attendee are dead.

“President Trump thanks law enforcement and first responders for their quick action during this heinous act,” spokesman Steven Cheung said in a statement. “He is fine and is being checked out at a local medical facility. More details will follow.”

The Secret Service said in a statement that “the former President is safe.”

Two officials spoke to The Associated Press on the condition of anonymity to discuss the ongoing investigation. They said the shooter was not an attendee at the rally and was killed by U.S. Secret Service agents.

Butler County district attorney Richard Goldinger said in a phone interview that the suspected gunman was dead and at least one rally attendee was killed.

Trump, the presumptive Republican nominee, was showing off a chart of border crossing numbers during his last rally before the Republican National Convention opens Monday when the apparent shots began.

As Trump was talking, a popping sound was heard. Trump said, “Oh,” and put his right hand up to his right ear as people in the stands behind him appeared to be shocked. Two more pops could be quickly heard and he crouched down.

Someone could be heard saying near the microphone at Trump’s lectern, “Get down, get down, get down, get down!” as agents tackled the former president. They piled atop him to shield him with their bodies, as is their training protocol, as other agents took up positions on stage to search for the threat.