The 19-year-old alleged Islamic extremist suspected of attacking NYPD cops with a machete on New Year’s Eve penned a disturbing manifesto that urged his family to “please repent to Allah and accept Islam,” police sources told The Post.

Trevor Bickford — a Maine resident who arrived in the Big Apple just days before the attack — carried the handwritten note in his backpack, along with a collection of religious material and $200 while staying at the Bowery Mission in Manhattan, the sources said.

“To my family — specifically, mother —  I’m sorry for not having been a good enough son,” the note read, according to a police source.

“I fear greatly that you will not repent to Allah,” it said. “And therefore I hold hope in my heart that a piece of you believes so that you may be taken out to the hellfire.

“To [my brother] Travis. Of anyone I’ve known who I have felt is closest to faith — it’s you,” he allegedly wrote. “Of anyone I’ve ever wanted to accept Islam with me — it’s you. Please repent to Allah and accept Islam. I fear for you.

“To [my other brother] Devon, there was a time when we were close, but that time has passed,” the manifesto said. “You have joined the ranks of my enemy. And for that I can give you no kind words – return to Allah.”

Bickford, of Wells, Maine, is believed to have become a radicalized Muslim in recent years following the overdose death of his father, Tom, who died in 2018 at the age of 41.

The teen’s father played a “very active” role in the lives of his three sons, and “could often be found coaching them at football and wrestling,” the Portland Press Herald reported.

Bickford’s radical shift put him on the FBI radar, and sources said his name surfaced on an FBI “Guardian Watchlist” before he hopped an Amtrak train and traveled to New York, arriving on Dec. 29, according to sources.

Around 10 p.m. on Saturday he allegedly attacked cops working the Times Square detail, including a rookie on his first assignment, police said.

The young cop, who was still assigned to the police academy, suffered a gash to his head, and a Staten Island officer suffered blunt force trauma to the head. Both were taken to Bellevue Hospital with non-life-threatening injuries.

Bickford was shot in the shoulder and wounded during the attack, police said. He remained hospitalized Sunday and has not yet been charged.

It is unclear how long Bickford had been staying at the Bowery Mission, but police sources said investigators found a sheath for the machete, a variety of other knives, and a collection of religious material.

According to reports, Bickford once appeared to be a typical American teenager who played on a championship football team at Wells High School, won an art award in school for his jewelry and made the honor roll as a freshman.