One person was killed and seven others injured in a shooting and stabbing at the Colorado Motorcycle Expo on Saturday, Jan. 30, 2016.

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DENVER -- No charges will be filed against an off-duty Colorado Department of Corrections employee who killed a man during a brawl at the Colorado Motorcycle Expo that left several others injured, the Denver District Attorney's Office announced Tuesday.

Victor Mendoza, 46, was killed by a gunshot wound during a fight between two motorcycle clubs at the Denver Coliseum on Jan. 30 and his death was ruled a homicide, the Denver medical examiner said.

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The fight broke out between The Mongols and the Iron Order motorcycle clubs. The investigation confirmed that shots were fired by Mendoza and Derrick Duran, the corrections department employee, the DA's office said.

Duran fired the first shot, injuring one person. Within a minute, Mendoza shot at Duran, grazing his torso and hitting another man behind Duran. Duran then fatally shot Mendoza.

The DA's office said four people were hit by gunfire, two people were victims of assault and one person was stabbed.

The Denver Police Department conducted hundreds of hours investigating the brawl and presented it to the district attorney's office on Monday as a first-degree murder case, Cmdr. Ron Saunier said at a news conference.

"(T)he legal review concluded that there is no likelihood of a conviction due to the self-defense claim of Mr. Duran," the DA's office said in a news release.

Duran was a member of the Iron Order club, while Mendoza was a Mongols club member.

Saunier said about 40 witnesses were talked to at the scene and at least 17 of them were with Iron Order, whose membership includes those from law enforcement agencies.

Saunier said the Iron Order witnesses were not current law enforcement members but some did have previous experience.

"We have considered this a homicide investigation throughout," Saunier said. "I believe we have done a complete and thorough investigation."

One wounded Mongols member did not talk to police and other members also declined to be interviewed.

In February, Stephen Stubbs, an attorney with The Mongols, said an Iron Order started a verbal, then a physical altercation.

“There’s no need to pull out weapons and escalate because you are losing a fistfight,” Stubbs said.

John Whitfield, a lawyer and member of Iron Order, said it was the Mongols who started the fight by jumping three outnumbered Iron Order members.