A motive is under investigation, but authorities are not ruling out that Bickford came to NYC specifically to attack officers.
MIDTOWN, Manhattan (WABC) -- The NYPD and the FBI are investigating after three officers were attacked by a man with a machete just blocks away from Times Square on New Year's Eve.
The attack on the officers is being investigated as a possible incident of terrorism because of online postings and the method of attack by the 19-year-old suspect, law enforcement sources told ABC News.
The attack happened near 52nd and 8th just after 10 p.m. on Saturday just hours before the ball dropped.
All three officers were hospitalized, one with a fractured skull and another with a bad cut, but were expected to recover. All three officers were released from the hospital on Sunday evening.
One of the officers was an eight-year veteran while the other was a rookie officer who just graduated from the police academy on Friday.
Moments after the attack, the suspect, who was later identified as Trevor Bickford, was shot in the shoulder by police. He was expected to recover.
He took an Amtrak train to New York on December 29, the sources said.
Bickford came to New Years Eve in NYC from Wells, Maine, and federal and local law enforcement officials are now starting to look through online postings that preliminarily indicate recent extremist Islamic radicalization, law enforcement sources told ABC News.
While his motive remains under investigation, the authorities are not ruling out that he came to NYC specifically to attack police officers, the sources said.
Investigators are pouring over the suspect's writings to determine motivation and history of radicalization, law enforcement sources told ABC News.
The mother and aunt of Trevor Bickford notified law enforcement in recent weeks about their concerns he was gravitating toward dangerous Islamist ideologies, the sources said.
Should authorities determine the attack was motivated by an Islamist ideology it would make it the first ever terror incident associated with New Year's Eve in Times Square, something the NYPD and FBI had long feared and prepared for.
The FBI's Joint Terrorism Task Force had previously looked into the suspect, law enforcement sources said, after he was reported by relatives.
The attack and sound of a gunshot briefly sent some people in the crowd running, but the incident did not impact the festivities in Times Square, which continued uninterrupted.
Mayor Eric Adams said at a news conference that he had spoken to one of the wounded officers as he was being stitched up at the hospital.
"He was in good spirits," Adams said. "He understood that his role saved lives of New Yorkers today."
The blocks where the biggest crowds gather to see performances and the midnight ball drop can only be accessed through checkpoints where officers use metal-detecting wands to screen for weapons. Large bags and coolers are banned. Barriers are set up to prevent vehicle attacks in the secure area.
The security perimeter can only extend so far, though. The attack took place on 8th Avenue, which is often packed with thick crowds navigating around the frozen zone or trying to find one of the secure entrances.
Both federal and local law enforcement stressed at an early morning news conference Sunday the attack that injured three NYPD officers appeared to be an isolated incident and there was no larger threat.
Prior to New Year's Eve, the NYPD noted in a pre-event assessment "Throughout December, multiple pro-ISIS users disseminated extremist propaganda graphics broadly calling for attacks in advance of the New Year, advocating a wide range of low-tech tactics."
Knife attacks have long been promoted by Islamist terror groups.
(The Associated Press contributed to this report.)
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