Enrique Marquez, a neighbor and friend of one of the San Bernardino shooters, will likely be charged as early as today in connection with the investigation, sources have told ABC News.

Federal officials plan to file criminal gun charges against the friend and former neighbor of one of the San Bernardino, Calif., shooting suspects who allegedly purchased the rifles used in the attack that killed 14 and wounded more than 20 this month, according to people familiar with the decision.

Federal prosecutors will bring criminal charges against the former neighbor and friend of the San Bernardino shooters who purchased two guns three years ago that ended up being used in the massacre earlier this month.

As investigators focus on what or who motivated San Bernardino shooters Syed Rizwan Farook and his wife, Tashfeen Malik, to open fire at the Inland Regional Center, a report about Malik's comments on social media before she moved to the U.S. is raising questions about how thoroughly she was vetted.

The brothers were a study in contrasts. Syed Raheel Farook was the extrovert — loud and sociable with an air of nonchalance. Acquaintances said he preferred to walk a casual line when it came to religion. He told people he "wasn't into Islam," dated a non-Muslim girl, imbibed freely and showed up at a local mosque primarily to please his family.

As FBI investigators return to search a San Bernardino lake today for clues into last week's deadly shooting, funerals continue for some of the 14 victims who lost their lives during the massacre in Southern California's Inland Empire.

An FBI dive team returned to a San Bernardino lake Friday with a metal detector, seeking evidence pinpointing the motive and history of the married attackers, including an apparent plot in 2012 that was never carried out.

As federal authorities attempt to piece together the circumstances surrounding last week's terrorist attack in San Bernardino, their far-flung investigation has taken them as far away as Pakistan and Saudi Arabia.