SAN BERNARDINO -- A federal law enforcement source said the FBI is investigating whether San Bernardino suspect Syed Rizwan Farook and his neighbor and in-law Enrique Marquez planned to commit a terrorist act in 2012 and then abandoned the plot, reports CBS News senior investigative producer Pat Milton.
Marquez legally purchased the assault weapons used in the San Bernardino attack.
The source said the FBI is looking into the possibility that the breakup of a plot to kill Americans in Afghanistan by four men in Riverside, California, in 2012 by the FBI may have caused Farook and Marquez to shelf their alleged plans.
Two of the men were convicted and two others plead guilty in connection to that Afghanistan plot.
After the San Bernardino attack, Marquez checked himself into a mental health facility.
Federal authorities are looking to charge Marquez with material support for terrorism, for his role in providing some of the weapons used in the attack.
CBS News has also learned that Marquez is related to the Farooks through marriage. He married the sister of Farook's brother's wife. The Farooks and Marquez were neighbors for years, but he married into the family last year. The women are Russian.
Farook and his wife, Tashfeen Malik, who authorities say are responsible for killing 14 people at a holiday party in San Bernardino, were radicalized at least two years ago and had discussed jihad and martyrdom as early as 2013, one year before they married, FBI Director James Comey said Wednesday.
CBS News' Jan Crawford reports that Marquez is now being questioned by the FBI over what he may have known about Farook and Malik's plans.
Comey told the Senate Judiciary Committee that investigators believe that Farook and Malik were radicalized even before they began their online relationship and that Malik held extremist views before she arrived in the U.S. last year.
He told the panel that the two "as early as the end of 2013 were talking to each other about jihad and martyrdom before they became engaged and married and were living in the U.S."
The disclosure means that Malik's radicalization had already begun when she applied for a visa to come to the U.S. to get married, and that the government's vetting process apparently failed to detect it. Comey said he didn't know enough to say whether weaknesses in the visa process enabled her to enter the U.S.
Also on Wednesday, the father of Malik said he condemns and regrets his daughter's action and the killings in San Bernardino.
Gulzar Ahmad Malik spoke to The Associated Press by telephone from Jiddah, Saudi Arabia. He says he is "very, very sad... I am in such pain that I cannot even describe it."
Gulzar Ahmed Malik has been a resident in the kingdom since the early 1980s, the Saudi Interior Ministry says.
Malik came to the United States in July 2014 from Pakistan after being approved for a K-1, or fiancee visa. Homeland Security Secretary Jeh Johnson has said the Obama administration is now reviewing the program. He did not say what changes were being considered.
Malik married Farook the following month. Farook was born in Chicago in 1987 and raised in southern California.
FBI officials had previously said that the couple had been radicalized for "quite some time," but the disclosure Wednesday was the most specific yet about the timeline of their relationship and progression toward extremism.
Comey said the couple was clearly inspired by a foreign terror organization, but that investigators did not yet know whether their online courtship was arranged by such a group or developed naturally on its own.