The FBI is leading the investigation into Saturday’s  assassination attempt on former President Trump.

They identified the dead gunman as 20-year-old Thomas Mathew Crooks of Bethel Park, Pennsylvania. Agents swarmed the shooter’s home overnight and found explosive materials. The FBI says he acted alone although the motive for the shooting remains unclear. A former classmate described Crooks as “a loner” who was frequently bullied in high school.

Multiple reports say the suspect used a semiautomatic rifle when he opened fire during a Trump campaign rally in Pennsylvania Saturday. President Biden said Trump had heightened Secret Service protection and a full review of the event will take place.

The U.S. Secret Service is facing intense scrutiny following the assassination attempt on former President Trump. Lawmakers on both sides of the aisle are asking how a sniper was able to get on a rooftop about 400 yards from the stage and fire shots at Trump. There are also questions about the size of the rally security perimeter and what efforts agents took to sweep the shooter’s building.

President Biden said he had a “short but good conversation” with Trump yesterday and added that he and his wife are keeping him and his family in their prayers. Biden condemned the attack again, saying “an assassination attempt is contrary to everything we stand for as a nation.” He also cautioned people against making “assumptions about [the shooter’s] motives or his affiliations.”

The spectator who was killed at the rally was identified by family members as 50-year-old Corey Comperatore, a former fire chief who lived in Sarver, Pennsylvania.   He was hit while shielding his family from the gunfire, and Pennsylvania Governor Josh Shapiro said “Corey died a hero.”