WASHINGTON -- Authorities said Wednesday the two killers in the San Bernardino attack -- American Syed Farook and his Pakistani wife, Tashfeen Malik -- may have had help from a third suspect.
FBI Director James Comey told Congress the couple had become radicalized several years ago.
"As early as the end of 2013, they were talking to each other about jihad and martyrdom before they became engaged and then married and then lived together in the United States," Comey said.
The radicalization could include Enrique Marquez -- a friend who is related to Farook by marriage.
A U.S. official told CBS News the FBI is investigating whether Farook and Marquez were planning a violent attack as far back as 2012, and discussed buying weapons.
A round of terrorism arrests in California in late 2012 may have scuttled the alleged plan.
Marquez eventually bought the two assault weapons used in last week's attack. He now is being questioned by the FBI over what he may have known about Farook and Malik's plans.
The FBI says the couple was on the path to radicalization even before ISIS rose to power -- and before Malik entered the United States last year to marry Farook on a visa that required an extensive background check.
At the Senate hearing Wednesday, New York Democrat Chuck Schumer asked if there were missed warnings.
"How come we didn't know about these communications before the attacks?" Schumer asked
South Carolina Republican Lindsay Graham asked whether their marriage was part of the plot.
"Is there any evidence that this marriage was arranged by a terorist organization or a terrorist operative?" Graham asked Comey.
The FBI director responded, "I don't know the answer to that yet."
"Do you agree with me that if it was arranged by a terrorist operative or organization, that is a game changer?" Graham asked.
"It would be a very, very important thing to know," Comey acknowledged.
Sources told CBS News the Justice Department is looking to charge Marquez with material support for terrorism. As the investigation continues, there could be other charges.