Newly released police reports show a Colorado corrections officer who killed a man during a shootout at a Denver motorcycle show told investigators he fired the first shot because he was being punched and cornered.

A 195-page report released Tuesday says police proposed charging Derrick Duran with first-degree murder in the January brawl. But prosecutors refused because his self-defense claim made it unlikely a jury would convict him.

Duran, a member of the Iron Order motorcycle club made up mostly of police and military, says the violence started when members of the Mongols club attacked his group. Duran says he pulled his gun to get them to stop and fired as a Mongol kept punching him in the face.

That started a gunbattle that left Mongols member Victor Mendoza dead and seven others shot, beaten or stabbed.