Utah prosecutors have charged 22-year-old Robinson with aggravated murder in the killing of Charlie Kirk. The charge could carry the death penalty if he is convicted of the September shooting. Utah County Attorney Jeff Gray said the murder of Charlie Kirk is an American tragedy.

Prosecutors allege that Robinson fired a bolt-action rifle at Kirk in the neck from the roof of a campus building as he spoke with students on September 10 at a Utah university. He also faces counts of felony discharge of a firearm, punishable by up to life in prison, and obstructing justice, punishable by up to 15 years. Kirk, a prominent conservative figure who founded Turning Point USA, was shot during a campus event and died soon after.

Robinson was arrested late on Thursday near St George, the southern Utah town where he grew up. Investigators conducted a search of his family home in Washington, Utah, about 240 miles south-west of the shooting location. Authorities are trying to establish a motive and whether anyone else was involved. FBI Director Kash Patel said DNA evidence linked Robinson to a towel-wrapped rifle found near the Utah Valley campus and a screwdriver recovered from the rooftop where the fatal shot was fired. He also said the FBI is examining a Discord gaming chatroom with more than 20 people connected to Robinson to identify others involved. Utah Governor Spencer Cox noted disclosures about Robinson’s social media activity and political views and said more information could emerge at the initial court appearance. Beaux Mason, the state DPS commissioner, said Robinson’s partner has cooperated and investigators believe the suspect acted alone but are checking whether anyone else knew of his plans.