By Robin Levinson King

Copyright bbc

FBI special agent in charge Robert Bohls said they had recovered the suspected weapon – an imported Mauser .30-06 bolt action rifle – in a wooded area near the scene wrapped in a towel, as well as a palm print and a “footwear impression”.

He told a news conference on Thursday they do not think there is a risk to the community in the city of Orem, 40 miles (64km) south of Salt Lake City.

Utah Department of Public Safety Commissioner Beau Mason said the gunman – who has not been publicly identified – “appears to be of college age”, and had blended well into the campus environment.

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Investigators say the suspect arrived on campus at 11:52 local time on Wednesday – just under half an hour before Kirk was killed with a single shot at around 12:20.

The gunman reached his position by climbing the stairwells to the roof and then making his way across to the shooting location. After opening fire, he jumped off the building and escaped, officials said.

A motive for the shooting is still unknown, though Utah Governor Spencer Cox called it a “political assassination”.

Kirk, who frequently held debates and speaking events on university campuses, was addressing a crowd of about 3,000 people and discussing gun violence in the US in the moments before he was shot.

“Do you know how many transgender Americans have been mass shooters over the last 10 years?” an audience member asked at the event, titled Prove Me Wrong.

“Too many,” replied Kirk.

The questioner said there had been five in 10 years and asked Kirk how many mass shooters there had been in that time.

“Counting or not counting gang violence?” Kirk replied before gunfire rang out.