The FBI released a video of the shooter who killed Charlie Kirk at Utah Valley University on Wednesday.
The video shows the suspect jumping from a rooftop and running away from the scene following the shooting.
According to the FBI, trace evidence collected from the rooftop includes shoe impressions, a forearm imprint, and a palm print.
The shooter's weapon and ammunition were recovered from a wooded area near the campus, the FBI added.
The FBI released a photo of the main suspect during a briefing on Thursday.
The FBI also offered a reward of up to $100,000 for information leading to the identification and arrest of the person or people responsible for the shooting.
FBI asks public to assist in identifying suspect
The FBI is asking the public to assist law enforcement in identifying the suspect.
The shooter has not been publicly identified, but the FBI circulated grainy images apparently taken from security cameras showing a "person of interest" wearing a black top, black sunglasses, and a dark baseball cap. The top appears to have an image of a bald eagle flying across a US flag.
FBI and state officials said the killer arrived on the campus a few minutes before the event began, a debate led by Kirk titled "Prove Me Wrong" outdoors in front of about 3,000 people at Utah Valley University in Orem, Utah, about 40 miles (65 km) south of Salt Lake City.
This is a developing story.