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

The Secret Service said it killed the suspected shooter, 20-year-old Thomas Matthew Crooks, who attacked from an elevated position outside the rally venue.

The FBI named Crooks, of Bethel Park, Pennsylvania, as the subject involved in the assassination attempt. The agency said the investigation remains active and ongoing.

Records show Crooks was registered as a Republican voter in Pennsylvania, but federal campaign finance reports also show he gave $15 to a progressive political action committee on Jan. 20, 2021, the day President Joe Biden was sworn in to office.

One attendee was killed and two were critically injured. Trump said on social media that a bullet “pierced the upper part” of his right ear before agents whisked him off stage.