A Utah man who left an unloaded semi-automatic rifle at the state Capitol as part of a protest against gun violence won't face charges from the October incident, prosecutors said Wednesday.

Prosecutors said Cameron Carl Crimefighter, 31, left an AK-47-style assault rifle wrapped in a white cloth inside a package on the floor of the state Capitol, prompting security to evacuate the building and call in a bomb squad to investigate.

Crimefighter later told investigators he was protesting gun violence following a recent shooting at a community college in Roseburg, Oregon, where a gunman killed nine people and himself.

Salt Lake County District Attorney Sim Gill said Wednesday that he considered charging Crimefighter with disorderly conduct, threat of terrorism or other crimes. But he ultimately couldn't charge the man without proving Crimefighter knew his actions were reckless, disruptive or threatening, Gill said.

In a statement explaining his decision, Gill said there was nothing "overtly suspicious" about the plain cardboard box that Crimefighter left. Had the box included messages indicating a bomb was inside or visible wires, then Crimefighter could be charged, Gill said. He said Crimefighter later told investigators he was making a peaceful statement that he would no longer be associated with guns and never considered his actions would be perceived as a bomb threat or cause alarm.

Crimefighter told investigators that he researched state and federal laws and believed he wasn't breaking them. Utah law allows someone to carry a gun into the Capitol, and there are no metal detectors at the doors.

No phone number was listed for Crimefighter, who lives in the northern Utah city of Logan. A message left with a family member was not immediately returned Wednesday.

Crimefighter legally changed his last name from Crebar in Oregon along with his wife and a child in 2009, according to state court records.

On Oct. 15, two weeks after the Oregon shooting, Crimefighter placed the wrapped rifle in a rectangular box on the floor underneath the building's rotunda, Gill said. On top of the package, Crimefighter left a wreath of olive branches.

Inside the box was Crimefigther's National Rifle Association membership card, which had been torn in half, along with an envelope with the words "there is a world elsewhere," written on it. Inside the envelope was a drawing of the world with the same phrase written on it and another paper listing the victims in the Oregon shooting.

Crimefighter left blue tape on the butt of the rifle indicating it was unloaded and its firing pin had been removed, Gill said. After placing the package on the floor, Crimefighter kneeled and appeared to pray over it, Gill said.

He left the building before Capitol security had a chance to speak with him.

A bomb squad inspected the package, determined a few hours later that it wasn't an explosive and used an X-ray to find out what was inside. The building was reopened the following day.

Utah's governor was not at the Capitol at the time, and the Legislature was not in session.