The Uzbeki national accused of killing eight people on the Lower West Side bike path was so loyal to ISIS that he asked if he could fly the terror group’s flag inside his Bellevue Hospital room, authorities revealed Wednesday.

Sayfullo Saipov also boasted that “he felt good” about the Tuesday afternoon pickup truck attack, which injured 18, according to a federal criminal complaint.

Federal prosecutors said Saipov was inspired to commit mass murder by watching hours of ISIS snuff films on his cellphone, and had been plotting the heinous attack for at least a year.

“In particular, Saipov was motivated to commit the attack after viewing a video in which [ISIS leader] Abu Bakr al-Baghdadi . . . questioned what Muslims in the United States and elsewhere were doing to respond to the killing of Muslims in Iraq,” the complaint says.

Saipov, 29, first arrived in the United States from Uzbekistan in 2010. Neighbors and public records paint the accused killer as a longtime “radical” who didn’t pay his taxes, ignored warrants and freaked out his own imam with his emotional intensity.

He always seemed to be carrying a dark secret, according to José Mejia, 49, who lives near Saipov’s current address in Paterson, NJ.

“He always looked like he was hiding something,” the neighbor told The Post.

“I’d see him a couple times with some people, I didn’t know if it was family or friends. Just from the way he looked, I thought he seemed very secretive.”

And Saipov’s 24-year-old wife, Nozima Odilova, apparently shared his gruff nature, according to neighbor Maria Rivera, 47, who recalled an icy reception when she found one of the couple’s two young daughters wandering the neighborhood and returned the girl home.

“I said, ‘Listen, your daughter, she was in the middle of the street,’ ” Rivera recalled. “And she didn’t say nothing to me. She walked inside the house. No ‘Thank you,’ no nothing.”

A Florida imam said he was distressed by Saipov’s behavior shortly before the terror suspect moved to New Jersey this year.

“I used to tell him, ‘Hey, you are too much emotional,’ ” the imam, named Abdula, told the New York Times

“He did not learn religion properly. That’s the main disease in the Muslim community.”

Saipov’s intensity accelerated over the last year, according to the criminal complaint, which states that he began planning his attack a year ago by watching ISIS training videos.

The federal complaint says he had about 90 videos that included “what appear to be ISIS fighters killing a prisoner by running the prisoner over with a tank.”

Other footage featured “ISIS fighters shooting a prisoner in the face . . . a video of a beheading . . . [and] instructions for how to make a homemade improvised explosive device,” the complaint says.

Saipov’s cellphone “also contains approximately 3,800 images, many of which appear to be ISIS propaganda.”

One day after the bike-path massacre, Saipov reveled in his own bloodshed.

“Saipov requested to display ISIS’s flag in his hospital room and stated that he felt good about what he had done,” the complaint states.

Saipov, who was shot in the stomach by police, was wheeled into a Manhattan federal courtroom Wednesday evening shackled at his legs and feet.

Magistrate Judge Barbara Moses read him his rights and he answered the mainly yes-or-no questions through a Russian interpreter — piping up himself once to say “Thank you” in broken English when the judge approved his request for a court-appointed lawyer.

He was held without bail.

The complaint against Saipov does not say when or where he was radicalized.

He “was admitted to the US upon presentation of a passport with a valid diversity immigrant visa to US Customs and Border Protection in 2010,” according to a statement from the Department of Homeland Security.

His first stop was Cincinnati, where he stayed with family friends for two weeks. Even then, it was clear something was off, according to foster family member Dilnoza Abdusamatova.

“He always used to work,” she told the Cincinnati Enquirer. “He wouldn’t go to parties or anything. He only used to come home and rest and leave and go back to work.”

He bounced between Florida and Ohio, racking up several traffic tickets along the way.

He was in Ohio by the end of 2011, according to truck driver and Uzbek national Mirrakhmat Muminov, who remembered him as “not happy with his life.”

“He had the habit of disagreeing with everybody,” Muminov said.

In August 2012, he copped a guilty plea to two traffic violations in Pennsylvania, records show.

He and his wife, Odilova, married in 2013, records state. They have two daughters, and Odilova also may have given birth to a son over the summer, according to the imam, Abdulla.

The state of Ohio put a lien against Saipov in August 2015 for failing to pay $400 in back property taxes, but he had already moved to Florida, records show.

In December 2015, he was ticketed for driving in Missouri with faulty brakes. He never paid or even bothered to show up in court, and in April 2016, a warrant was issued for his arrest.

Missouri court records state he was served the warrant at his Tampa home late last year.



Additional reporting by Laurie Mizrahi, with wire services