LOS ANGELES — When the FBI went to speak with a man accused of buying the assault rifles used by his friend in the San Bernardino terror attack, they learned about a sinister plot the two men had crafted years earlier.
In interviews over 11 days, Enrique Marquez Jr. willingly told agents how he and Farook had planned to slaughter students at a community college they attended and massacre motorists on a gridlocked freeway, according to court documents.
Marquez, the only person arrested in connection with the Dec. 2 shootings carried out by Farook and his wife, is now facing his most serious charge in the plot that fizzled years ago.
Marquez, 24, is charged with conspiring to provide material support to terrorists for the alleged plots in 2011 and 2012 that he never acted on.
"The material support provision is sort of the prosecutor's weapon of choice in going after individuals in plots like this," said William C. Banks, interim dean the Syracuse University law school. "They'll have no problem applying that to this guy's activities."
If convicted of the charge, Marquez could face up to 15 years in federal prison. He also faces counts related to purchasing a gun used in the San Bernardino attack and to a sham marriage to help a Russian relative of Farook get immigration papers, prosecutors said. Each of those charges carry 10-year maximum penalties.
Marquez is being held without bail and has not entered a plea in the case. His lawyer would not comment Friday.
The federal terror-related charge faced by Marquez is slightly different than one by the same name used in most recent cases charging suspects with conspiring to provide material support to terrorists, said Bobby Chesney, a University of Texas law professor.
Dozens of cases filed in the past year target people caught by law enforcement in the process of becoming radicalized and planning to go overseas or provide some other aid, such as money, to a specific terrorist group. That version of the law does not require prosecutors to prove the help is going toward a specific violent act, just a specific organization.
Marquez is charged under an older version of the offense not used as often that must connect the material support with a specific violent act — whether it was carried out or not. Prosecutors don't have to show any affiliation with a terrorist group.
"Obviously, there are many more instances of people trying to join up with a group rather than being linked to actual violent acts," Chesney said.
An FBI affidavit filed with the charges against Marquez said he bought rifles for Farook in 2011 and 2012 so they could kill students at Riverside City College and drivers on State Route 91, an infamously congested nearby freeway.
The plot may never have been discovered if Farook, 28, and his wife, Tashfeen Malik, 29, had not used guns that authorities say Marquez bought and used to kill 14 people and wound 22 at a holiday meeting of Farook's health department co-workers.
The FBI has labeled the shootings terrorism, making it the deadliest strike by Islamic extremists on American soil since Sept. 11, 2001.
Marquez allegedly called 911 hours after Farook and Malik died in a police shootout to say that his guns had been used in the attack. He then showed up at a hospital emergency room after drinking nine beers and said he was "involved" in the shooting, authorities said. He was involuntarily committed to a psychiatric unit.
The FBI said he spoke with agents over 11 days, waiving his rights to keep quiet or consult a lawyer.
Attorney E. Martin Estrada, a former federal prosecutor in Los Angeles, said the criminal complaint was unusual in the lengths the FBI went to state that there was no evidence Marquez was involved in the San Bernardino shootings and also making it clear that he had spoken willingly to agents.
Experts said that evidence will be difficult for a defense lawyer to challenge and would make it difficult to defend Marquez.
"It's a prosecutor's dream," Banks said.
Suspects often start off talking with law enforcement officers but eventually clam up.
The FBI said Marquez signed a statement each day waiving his right to a lawyer.