The former neighbor of San Bernardino gunman Syed Rizwan Farook reportedly spoke to regulars at his job about “sleeper cells just waiting” to attack the United States.

A frequent customer at Morgan’s Tavern, where Enrique Marquez worked, told The New York Times on Friday that nobody took Marquez seriously when he spoke of terror attacks and had no clue he was a figure in the investigation into the massacre at an Inland Regional Center office building that left 14 people dead.

“We took it as a joke. When you look at the kid and talk to him, no one would take him seriously about that,” Nick Rodriguez told The Times.

Federal authorities are expected to bring charges against Marquez, 24, who supplied Farook at least two of the weapons used in the attack. He legally purchased the AR-15 rifles Farook and his wife Tashfeen Malik used on their killing spree on Dec. 2. He will likely be indicted after spending hours talking to investigators about Farook and Malik.

Authorities believe Farook and Marquez discussed executing an attack somewhere in the Los Angeles area in 2012, but decided not to go through with it after four people were arrested in nearby Riverside County in an unrelated terror case. Investigators believe Marquez bought the rifles and gave them or sold them to Farook in preparation for that planned attack. It’s unclear what the target of the attack would’ve been.

It was not immediately clear what specific charges Marquez would face, but Fox News has learned that he is the only person expected to be indicted anytime soon in connection with the attack. However, authorities say that other subjects are being monitored.

Marquez began speaking with federal authorities after they raided his mother's home over the weekend. Right after the shootings, Marquez called his mother to say he was safe, but that he wouldn't be coming home, neighbor Lorena Aguirre told the Associated Press. He later checked into a mental health facility. It's unclear where he is now.

Marquez is also related to Farook by marriage, having wed the sister-in-law of the gunman's older brother, state records show. The Associated Press reported that Marquez and and his bride, Mariya Chernykh listed their address on the marriage license at the same Corona home where Syed Raheel and Tatiana Farook live. Viviana Ramirez, a friend of Marquez, told the Los Angeles Times that Marquez rarely spoke about his family or his marriage.

Azmi Hasan, the mosque's facilities manager, said Wednesday that he understood Marquez had converted to Islam, but said he was not a member of that mosque. Marquez had only worshipped there three to four times over seven years, said Hasan, who hadn't seen him in about four years.

Marquez had a security guard license in California for several years, but it expired last year. He had worked at Wal-Mart since May, but has since been fired, spokesman Brian Nick told the Associated Press.

He spoke of wanting to join the military, a fellow student at Riverside Community College told the Los Angeles Times. His brother-in-law, Raheel Farook, is a Navy veteran, serving from 2003 to 2007 and earning the Global War on Terrorism Expeditionary Medal and the Global War on Terrorism Service Medal, among other awards.

Investigators were also examining the digital footprint left by the shooters, who tried to destroy their computer hard drives and cell phones prior to carrying out the attack. Investigators tell Fox News the data that has been recovered shows that Farook posted multiple messages online expressing support for Islamist groups like Muslim Brotherhood and Hamas, while also expressing hatred for Israel. Investigators have also expressed concern that Farook may have been in contact with other terror groups.

Authorities used dive teams to search a lake in San Bernardino on Thursday and Friday. Investigators apparently found something in the lake, but have not announced what the object was. Investigators are looking for a hard drive that may have been dumped in the lake, a law enforcement official briefed on the investigation told The Associated Press.

The FBI investigation into the mass shooting has been one of the most comprehensive in the bureau's recent history. Law enforcement sources tell Fox News that more than 300 interviews related to the shooting have taken place in the U.S. An FBI team has also been dispatched to Europe as part of the investigation.

Fox News’ Adam Housley and The Associated Press contributed to this report.

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