Two years before Ahmad Khan Rahami went on a bombing rampage in New York and New Jersey, his father told the police that the son was a terrorist, prompting a review by federal agents, according to two senior law enforcement officials.
Separately on Tuesday, another official said that when Mr. Rahami was captured during a shootout with the police, he was carrying a notebook that contained writings sympathetic to jihadist causes.
In one section of the book, which was pierced by a bullethole and covered in blood, Mr. Rahami wrote of “killing the kuffar,” or unbeliever, according to the official, who agreed to speak about the investigation only on the condition of anonymity.
After Mr. Rahami was captured on Monday morning, ending one of the largest manhunts in the city’s history, investigators have turned their focus to what might have motivated, inspired or led him to plant bombs in the Chelsea section of Manhattan and on the Jersey Shore.
Officials are also looking at whether he had any assistance in building the bombs or if anyone knew what he was doing and failed to report it.
Of particular interest to the authorities is a series of trips Mr. Rahami made to Pakistan, once staying for nearly a year.
The father made the statement about his son being a terrorist to New Jersey police in 2014, when Mr. Rahami was arrested after a domestic dispute and accused of stabbing his brother.
The information was passed to the Joint Terrorism Task Force led by the Federal Bureau of Investigation in Newark. Officers opened what is known as an assessment, the most basic of F.B.I. investigations, and interviewed the father, who then recanted.
An official, when asked about the inquiry, said the father made the comment out of anger at his son.
It is not clear if officers interviewed Ahmad Rahami.
On Tuesday morning, outside the family’s restaurant in Elizabeth, the father, Mohammad Rahami, told reporters, “I called the F.B.I. two years ago,” he said, shaking his fingers in the air.
Asked if he specifically meant his son, Mr. Rahami stormed away. A short time later, he responded to a reporter who asked, “Do you think your son is a terrorist?”
“No,” Mohammad Rahami said. “And the F.B.I., they know that.”
Ahmad Rahami spent over three months in jail on charges related to the domestic dispute, according to a high-ranking law enforcement official with knowledge of the investigation. A grand jury, however, declined to indict Mr. Rahami. Assistant Director William F. Sweeney, who heads the F.B.I.’s New York office, alluded on Monday at a news conference to a “domestic incident” in which he said the “allegations were recanted.”