The man accused of ramming a truck into people on a New York City bike path placed a call immediately before he carried out the attack on Tuesday afternoon, a law enforcement official told ABC News.
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The call was placed to Mukhammadzoir Kadirov, who is described by sources as a friend of suspected attacker Sayfullo Saipov. Kadirov is not being called a suspect.
The significance of the call Saipov made to Kadirov is not known.
The FBI had released a poster Wednesday asking for the public's help to find Kadirov when he initially could not be located. But, less than an hour after the poster went public, Assistant Director in Charge Bill Sweeney announced that agents were no longer looking for Kadirov.
At least eight people were killed in Tuesday's incident, which is being investigated as a terror attack, and another 12 were injured.
Saipov, 29, was allegedly "inspired" to commit the attack after watching ISIS videos on his cellphone and he "wanted to kill as many people as he could," according to a federal criminal complaint filed Wednesday by prosecutors in the U.S. District Court for the Southern District of New York.
Saipov wanted the black-and-white flag of ISIS displayed in his hospital room after allegedly revealing to authorities he had planned to strike more people on a bridge had he not crashed into a school bus, according to the complaint.
“During the interview with law enforcement, 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 allegedly rented the truck from a Home Depot in Passaic, New Jersey, Tuesday around 2 p.m. ET. He exited the bridge at 2:43 p.m. and drove southbound on the West Side Highway in New York City, according to license plate readers on the George Washington Bridge.
Shortly after 3 p.m., Saipov allegedly began plowing into cyclists and pedestrians on a bike path in lower Manhattan near West Houston Street and the West Side Highway. The suspect then drove south for about a mile, leaving behind strewn bodies and crumpled bicycles, police said.
The suspect crashed into a school bus near Chambers Street, just across from Stuyvesant High School. He emerged from the car with a paintball gun and a pellet gun, allegedly shouting "Allahu Akbar," an Arabic phrase that translates to "God is Greatest," before being shot in the abdomen by NYPD officer Ryan Nash, authorities said.
Saipov was transported to a hospital for treatment and is expected to survive. Officials say he acted alone.
City officials announced Thursday that the transportation department would begin to install concrete blockers in 57 spots along the bike path lining the West Side Highway beginning at 59th Street and heading into lower Manhattan. This will prevent cars from accessing the path but allow bikes and joggers to do so, they said.
Two cellphones, a stun gun, a document with text in Arabic and English and a black bag containing three knives were recovered from the truck. Saipov allegedly admitted to writing the document and told authorities the cellphones belonged to him, according to the criminal complaint.
One of the cellphones contained 90 videos, most of which appear to be "ISIS-related propaganda," including one with instructions on how to make an improvised explosive device, the complaint states.
Saipov was wheeled into court for his initial appearance before a judge Wednesday night. He was charged with providing support to ISIS and violence and destruction of motor vehicles, making him eligible for the death penalty. A plea was not entered.
Saipov has a preliminary hearing scheduled for Nov. 15 at 10 a.m. ET.
"He did this in the name of ISIS, and along with the other items recovered at the scene was some notes that further indicate that," John Miller, NYPD deputy commissioner of intelligence and counterterrorism, said Wednesday morning. "He appears to have followed almost exactly to a 'T' the instructions that ISIS has put out in its social media channels before with instructions to their followers on how to carry out such an attack."
Saipov was born in Uzbekistan. He entered the United States through New York's John F. Kennedy International Airport in 2010, according to law enforcement sources. He had a green card that allowed him permanent legal residence in the country, sources said.
The green card came via a government program called the Diversity Visa Lottery, which hands out about 55,000 visas per year.
After entering the country, Saipov first lived in Ohio before moving to Tampa, Florida. He then moved to Paterson, New Jersey, where he has lived with his wife and three children for several years, according to law enforcement sources.
During an interview with law enforcement while in custody, Saipov allegedly revealed that he began planning an attack in the United States about a year ago. He allegedly decided to use a truck "to inflict maximum damage against civilians" and rented one prior to Tuesday's attack to "practice making turns" with the vehicle, according to the criminal complaint.
"Saipov planned to use the truck to strike pedestrians in the vicinity of the West Side Highway and then proceed to the Brooklyn Bridge to continue to strike pedestrians. Saipov wanted to kill as many people as he could," the complaint states. "Saipov wanted to display ISIS flags in the front and back of the truck during the attack, but decided against it because he did not want to draw attention to himself."
Saipov allegedly chose to carry out the attack on Halloween "because he believed there would be more civilians on the street for the holiday," the complaint states.
He was allegedly motivated to commit the attack after watching 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," according to the complaint.
ABC News' Mark Crudele, Tara Fowler, Joshua Hoyos, Aaron Katersky, Josh Margolin, Mark Osborne and Emily Shapiro contributed to this report.