Two years before the bombings that Ahmad Khan Rahami is suspected of carrying out in New York and New Jersey, his father told the police that his son was a terrorist, prompting a review by federal agents, according to two law enforcement officials.
The father, Mohammad Rahami, in a brief interview on Tuesday, said that at the time he told agents from the Federal Bureau of Investigation about his concern, his son had just had a fight with another of his sons and stabbed the man, leading to a criminal investigation.
“Two years ago I go to the F.B.I. because my son was doing really bad, O.K.?” he said. “But they check almost two months, they say, ‘He’s O.K., he’s clean, he’s not a terrorist.’ I say O.K.”
He added: “Now they say he is a terrorist. I say O.K.”
It is not clear if officers ever interviewed Ahmad Rahami, but as investigators turn their focus to what might have motivated, inspired or led him to plant bombs in Chelsea in Manhattan and on the Jersey Shore, new clues are emerging indicating that he may have been increasingly receptive to extremist ideology.
When Mr. Rahami was captured during a shootout with the police on Monday, the authorities found a notebook, pierced with a bullet hole and covered in blood, expressing opinions sympathetic to jihadist causes, according to a law enforcement official who agreed to speak about the investigation only on the condition of anonymity.
In one section of the book, Mr. Rahami wrote of “killing the kuffar,” or unbelievers, the official said. Mr. Rahami also praised Anwar al-Awlaki, Al Qaeda’s leading propagandist, who died in a drone strike in Yemen, as well as the soldier in the Fort Hood shooting, one of the deadliest “lone wolf” attacks inspired by Al Qaeda.
Five years after his death in a drone strike in Yemen ordered by President Obama, Mr. Awlaki remains a powerful influence on would-be jihadists, especially in the English-speaking West. Among his documented admirers were Syed Rizwan Farook, who along with his wife killed 14 people in San Bernardino, Calif.; Omar Mateen, who fatally shot 49 people in an Orlando nightclub; and Tamerlan and Dzhokhar Tsarnaev, who staged an attack at the finish line of the Boston Marathon with pressure-cooker bombs in 2013.
Thousands of Mr. Awlaki’s lectures and jihadist declarations are available on the web, as is Inspire magazine, which has published detailed instructions for making pipe bombs as well as more sophisticated explosive devices using pressure cookers and Christmas lights, the same components used in the New York-area bombs.
One key area of investigation is around the question of whether Mr. Rahami had any help building the bombs or if anyone knew what he was doing and failed to report it. In all, he is linked to 10 explosive devices found in the region, including the two pressure-cooker bombs, one of which exploded in Chelsea on Saturday night, injuring 29 people.
The authorities are also looking into a series of trips Mr. Rahami made abroad between 2010 and 2014, including to Pakistan, where he once stayed for nearly a year. While the authorities said that they did not believe he was part of a larger terror cell operating in the region, they were looking for any evidence that might link him to a larger terrorist network.
Mr. Rahami’s 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 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.
Ahmad Rahami spent over three months in jail on the assault charges, 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.”