Gonzalez, 55, former president of the Vagos' Nicaraguan chapter, is accused of killing Jeffrey "Jethro" Pettigrew, who was the president of the Hells Angels' chapter in San Jose, California. He faces murder, conspiracy and other charges.
Gonzalez has been jailed since authorities say he was found hiding in a car on the downtown campus of the University of San Francisco in the days after the shooting. He told campus officers he was terrified someone was after him.
For the first time since his arrest, Gonzalez appeared in court Monday in a dark blue suit and tie instead of a jail jumpsuit. He entered his plea after the judge accepted Villagrana's plea deal.
"Definitely not guilty," Gonzalez told the judge.
David Houston, Gonzalez's lead attorney, said Villagrana's guilty plea was an "appropriate development."
"We're not pleading, because our client is innocent," Houston told The Associated Press.
Karl Hall, Washoe County's chief deputy district attorney, declined to comment in detail on Villagrana's plea agreement but told the AP, "I wouldn't have done it if I didn't think it was fair."
Villagrana was accompanying Pettigrew at an annual motorcycle rally in Reno-Sparks that attracted both gangs to the hotel-casino where the melee broke out. Prosecutors said they have security video of Villagrana shooting a Vagos member in the leg.
David Chesnoff, Villagrana's lead lawyer, told reporters after the judge accepted the plea deal that Villagrana was "sorry things turned out the way they did."
"He wasn't intending having these events occur," Chesnoff told KRNV-TV. "He lost his best friend, and that's a big deal to him."
Another Vagos member who police blamed for starting the fight that led to the killing pleaded guilty in March to second-degree murder. Sentencing is set for Aug. 22 for Gary Rudnick, former vice president of the Vagos' chapter in Los Angeles.
The judge granted the prosecution's request to keep secret the names and other information about all potential jurors, referring to them only by their juror number.
Hall said the extra precaution was needed because the suspects allegedly are members of "outlaw motorcycle gangs consisting of thousands of members worldwide."
"The potential for placing a juror or witness in danger is great," he said.