RIVERSIDE, Calif. -- The gunman who massacred his co-workers in the San Bernardino rampage and the friend who bought the assault rifles used in the shooting were related through marriage and may have plotted an attack together three years ago.

New revelations from officials and public records show a much deeper connection between Syed Rizwan Farook and Enrique Marquez than previously was disclosed.

Marquez purchased high-powered weapons at least three years ago that Farook and his wife fired when they burst into a holiday-themed meeting of Farook's fellow health inspectors Dec. 2, killing 14 people and wounding 21 others.

The FBI has said Farook's wife declared her allegiance to the Islamic State in a Facebook posting shortly before the attack began.

Farook, 28, and Tashfeen Malik, 29, were killed hours later in a shootout with police, leaving behind a 6-month-old daughter.

FBI director James Comey told the Senate Judiciary Committee on Wednesday the two shooters were radicalized well before Malik came to the U.S. on a fiancee visa. and they had discussed jihad and martyrdom as early as 2013.

Investigators are trying to determine whether Farook's path toward extremism predated that time and whether it led to plans to launch an attack in 2012, according to two people familiar with the investigation who were not authorized to discuss the matter publicly and spoke on condition of anonymity.

Marquez and Farook "were plotting an actual attack" that year, including purchasing weapons, but became apprehensive and shelved the plan because of law enforcement activity and arrests in the area, said Idaho Sen. Jim Risch, a Republican who sits on the Senate Select Committee on Intelligence.