In a plea deal criticized by the father of a victim, a California man pleaded guilty Thursday to providing the high-powered rifles used to kill 14 people in the San Bernardino terror attack.
Enrique Marquez Jr. appeared in federal court in Riverside with his hands cuffed and chained to his waist as a judge accepted his plea agreement with prosecutors.
Gregory Clayborn, the father of one of those killed, opposed the deal in remarks to the judge before the hearing.
"This man supplied these murderers with these weapons and he's going to get a slap on the wrist, your honor," Clayborn said, his voice cracking.
"My daughter, she didn't deserve this," he said.
Under the plea deal, Marquez could face up to 25 years in prison. A sentencing hearing before U.S. District Judge Jesus G. Bernal was scheduled for Aug. 21.
In addition to purchasing the weapons, Marquez, 25, of Riverside pleaded guilty to conspiring with one of the San Bernardino shooters in earlier mass killing plots targeting a community college and a gridlocked Southern California freeway that were never carried out.
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In court, Marquez sounded choked up after the prosecutor described what he had done. Marquez told the judge he had dropped out of high school and college but understood the allegations and the consequences of pleading guilty.
Victims' relatives were given tissue boxes ahead of the brief hearing. While Marquez was questioned, one sobbed. Another closed her eyes.
Afterward, Clayborn told reporters he believes Marquez knew about the San Bernardino attack that killed his daughter.
"To be surprised like this with what happened and this guy not being charged for the actual murders, it really made me angry," he said.
During court, Clayborn stood up and told the judge Marquez should never get out of prison.
"For him to get as light a sentence he got from the crimes that were committed based on what he provided to help that happen, it's a travesty and judicial system needs to fix it," he said.
U.S. attorney Eileen M. Decker said she understands why victims' relatives may feel the sentence is insufficient due to the pain they have suffered, but explained that she is bound by the law and there is no evidence that Marquez participated in or had advance knowledge of the San Bernardino attack.
But his purchase of the weapons and preparations with Farook for the attacks they never committed laid the foundation for the 2015 assault, she said.
"These chilling plans could have inflicted mass casualties. These plans thankfully were not executed," she told reporters outside the courthouse. "But there are connections between their planning in 2011 and 2012 that we believe assisted in the horrible attacks that took place in 2015."
Marquez was the only person criminally charged in the December 2015 attack that also left 22 people wounded at a meeting of San Bernardino County employees. Husband-and-wife assailants Syed Rizwan Farook and Tashfeen Malik were killed in a gunfight with authorities later that day.
Prosecutors said Marquez acknowledged being a "straw buyer" when he purchased two AR-15 rifles that Farook later used in his attack on the meeting of his San Bernardino work colleagues. Prosecutors have said Marquez agreed to buy the weapons because the pair feared Farook's Middle Eastern appearance might arouse suspicion.
Marquez also acknowledged plotting the college and freeway attacks with Farook in 2011 and 2012. He said he backed out of the plot after four men in the area were arrested on terrorism charges in late 2012, the FBI has said in court documents.
Marquez and Farook met in 2005 after Marquez moved next door to Farook's family in Riverside, about 55 miles east of Los Angeles.
Farook began educating his new friend about his Muslim faith and Marquez converted in 2007.
The FBI said the two began discussing extremist views shortly thereafter. By late 2011, Marquez spent time at Farook's home reading magazines published by al-Qaida and studying radical material online, federal officials said.
NBC4's Tony Shin and The Associated Press contributed to this report.