A driver plowed into a crowd in New York's Times Square midday Thursday, killing an 18-year-old woman and injuring 22 others, police said.
The motorist, a Navy veteran, tried to flee the scene, according to police, but was tackled by a traffic agent.
There is no indication of terrorism based on information at this time, Mayor Bill de Blasio said.
Police said the driver is in custody and this is believed to be an isolated incident.
A witness told ABC station WABC the scene was total "chaos" and "everybody was trying to help."
The car, a 2009 Honda Accord, struck 23 pedestrians, killing Alyssa Elsman, an 18-year-old tourist from Michigan, law enforcement sources and city officials said. Elsman graduated from Portage Central High School in 2016, her former principal said.
"Alyssa was the type of person who seemed very shy and reserved when you first met her, but once you started talking to her you realized she was smart, funny and engaging," principal Eric Alburtus said in a statement. "She will be deeply missed by the staff and students here."
The statement said the school will have grief counselors available on Friday "to help any students and staff who need support in processing this loss."
Police said 22 people were taken to nearby hospitals, including the 13-year-old sister of the deceased victim. Officials said four people are in critical condition, three others suffered serious injuries and the other 15 people have less serious injuries.
The driver was identified by police as Richard Rojas, 26, of the Bronx. At 11:55 a.m. he was driving south on 7th Avenue when he made a quick U-turn onto a sidewalk at 42nd Street and sped along the sidewalk for three-and-a-half blocks, striking multiple pedestrians until crashing at 45th Street, according to law enforcement.
After Rojas crashed, he fled the car but was detained by police and civilians, police said. He allegedly punched a police officer as they took him into custody, sources said.
The car appeared to catch fire after crashing.
Witness Annie Donahey told ABC News, "I was walking toward the subway station and the sidewalk that I was on was super crowded. Last minute I decided I was gonna cross the street ... I turn around because someone screamed. There's this red car, full speed, careening down the sidewalk."
Donahey said one woman she was walking next to before she crossed the street was struck by the car. "I looked back and she was in a pile on the street," Donahey said. "It could've been me."
She continued: "I wouldn't be here now if I hadn't crossed the street. It happened too fast."
"As a New Yorker you always worry about that kind of stuff but you always think it's never gonna happen to you," Donahey said. "It just made me feel so helpless.
"That stretch between 42nd and 43rd Street is always the most crowded. The fact that that's where he ended up going through was probably the most devastating place that he could've gone," she added. "And it's terrifying because I'm here all the time. It's just scary to know that that can happen, and it's surreal to know, and it feels personal."
Rojas has had multiple arrests, including two for driving while intoxicated, police said. Investigators are reviewing Rojas' criminal history and are in the process of interviewing him.
Law enforcement sources told ABC News initial tests have come back negative for alcohol but positive for drugs. Blood tests are underway to check for the presence of synthetic marijuana or PCP, among other substances, sources said. Sources also said police are trying to determine whether Rojas suffers from psychological problems, based on statements made at the time of his arrest.
Law enforcement sources said charges are pending.
Rojas is a veteran who served in the Navy from 2011 to 2014, sources said.
He has two prior arrests in Manhattan and Queens for driving while intoxicated; in one of those cases he was driving 90 mph in a 50-mph zone, law enforcement sources said. His most recent arrest was for menacing; Rojas is a notary and was arrested earlier this month for threatening someone who came to his home to get an annuity notarized, sources said.
The mayor said major sites in the city will get additional police coverage from anti-terror units.
New York Gov. Andrew Cuomo, who was at the scene getting briefed by New York Police Department officers, said in a statement, "Today’s events at Times Square were nothing short of horrific. I was briefed at the scene by Commissioner [James] O'Neill and saw firsthand the professionalism and diligence of New York’s first responders. As facts continue to emerge, my heart goes out to the victims of this terrible tragedy, as well as their families."
While there are some streets closed to traffic, Broadway theaters will be open tonight and will be accessible to pedestrians.
ABC News' Gio Benitez, Mark Crudele, Aaron Katersky, Erin Keohane, Josh Margolin, Will Gretsky and Jason Volack contributed to this report.