The FBI first became aware of Rahami in summer 2014, when local law enforcement contacted the agency's New Jersey field office about him, sources said. The FBI then opened a so-called "Guardian" file on Rahami, initiating the process to determine whether Rahami had any links to terrorism or other criminal activity, and whether a more formal investigation was warranted.
The assessment of Rahami produced no clear evidence or indications of radicalization, and at one point his father recanted his previous claims, sources said. Rahami he was not placed on any U.S. terrorism watchlists.
Speaking to reporters Tuesday outside of his New Jersey home, Rahami's father said he "called the FBI two years ago" about his son.
"I told them you got a connection with this guy," he said, without offering any further information. Though, he later said he didn't tell the FBI that his son was a terrorist, only that he was associating with "undesireables."
The FBI issued this statement Tuesday:
"In August 2014, the FBI initiated an assessment of Ahmad Rahami based upon comments made by his father after a domestic dispute that were subsequently reported to authorities. The FBI conducted internal database reviews, interagency checks, and multiple interviews, none of which revealed ties to terrorism."
Eyewitness News learned Ahmad Rahami was never questioned by FBI agents, and the father never directly told FBI agents that his son was a terrorist.
Instead, the father is said to have made the terrorist claim during a domestic dispute with his son. The son was brandishing a knife.
A neighbor heard the father order his son out of the house, and calling him a terrorist.
The neighbor's statement was passed to the FBI as part of the bureau's "guardian" program. That program pursues tips from the public about possible terror activity.
But the FBI's review never triggered placement on a government watch list, because their investigation found nothing to support it.
"We had a report of a domestic violence incident sometime ago. The allegations were recanted, we have no other information," said William Sweeney, Assistant Director FBI New York.
And the investigation was closed without agents ever directly interviewing Ahmad Rahami.
The FBI must have learned back then that Rahami had just come back from a year living in Afghanistan and Quetta Pakistan, a hotbed of extremism, that apparently wasn't a red flag either. A former Special Agent for the FBI explains why.
"We have hundreds, if not thousands, of people in similar situations that are from Afghanistan that are from Pakistan that travel to their home country for whatever reason, it's like trying to empty the ocean into the beach," said Manuel Gomez, Former FBI Special Agent.
Nevertheless, in some ways the 2014 case reflects how local, state and federal law enforcement agencies now seek to share and track threat-related information.
The fact that this latest suspected homegrown terrorist was captured alive provides law enforcement with a rare opportunity to find out first-hand how this once graduate of Edison High School, with plenty of friends and family, traveled down a path to radicalization.
"Have the ability to question him find out who his accomplices were, if he had accomplices, if he had any training or was completely self-radicalized off internet and find out how he got radicalized," said Karen Greenberg, the Center for National Security.
Click here to read more from ABC News.
Click here for more coverage of the bombings in Manhattan and New Jersey.