Federal authorities said Sayfullo Saipov drove ten blocks on a bike path at expressway-speed on a sunny Halloween afternoon, mowing down bikers and pedestrians. Among the dead are five tourists from Argentina who had traveled to New York to celebrate the 30th anniversary of their high school graduation.
Saipov left behind a note, handwritten in Arabic, which stated he acted on behalf of ISIS, according to investigators, who said they found that note near the truck he'd rented in New Jersey an hour before the attack.
Hours earlier, the NYPD scanner chirped the ominous alert: "Mass casualty incident. We got a mass casualty situation here."
At first, police thought it was a road-rage incident gone extreme, with the driver of this rental truck mowing down bicyclists and pedestrians.
The police view changed suddenly after witnesses told investigators the driver was yelling, "Allahu Akbar," or "God is Great," which has the become the jihadist battle cry.
Police said the driver ran from the scene right after it happened and was carrying pellet pistols. Officers shot Saipov in the abdomen with real guns. He underwent surgery on Tuesday.
"This was an act of terror, and a particularly cowardly act of terror, aimed at innocent civilians," said New York City Mayor Bill de Blasio. He said it targeted people "going about their lives who had no idea what was about to hit them."
Before the incident, Saipov wasn't on police radar or any terror list.
The I-Team learned that he came to the U.S. from Uzbekistan seven years ago and has no serious criminal history - only traffic violations in Pennsylvania and near St. Louis. A Missouri mugshot from a year ago shows Saipov when he was arrested for failure to pay a traffic fine. He recently lived in Florida with his wife and three children.
"We never feared anything because he had a family too," said former Tampa neighbor Melissa Matthews. "He was there with his wife and children. The children were young. I mean, he had a whole family as well. So no one ever suspected anything."
Truck-ramming is a tactic terrorist recruiters have pushed for years. Just this month, the I-Team found an ISIS magazine urging truck attacks.
Saipov also lived in Ohio for a time, but lately has been staying in Paterson, New Jersey, about 30 minutes from Manhattan. According to Uber, he had been working as a driver.
Federal agents have visited all his former homes, trying to figure out when he was radicalized and whether he had help.