RENO, Nev. (AP) – Detectives are reviewing witness accounts and “horrifying” cellphone video while they consider filing a criminal complaint after a pickup truck plowed into a crowd of people during a Native American rights demonstration in downtown Reno, the police chief said Tuesday.

The 18-year-old male driver and a 17-year-old passenger have been questioned but no arrests have been made in Monday evening’s incident on the street beneath the arch with the city’s famous slogan, “The Biggest Little City in the World.”

A 59-year-old woman remained hospitalized Tuesday with non-life threatening injuries. The driver, passenger and two others were treated for minor injuries, Reno Police Chief Jason Soto said.

A Facebook Live video of the protest shows a pickup truck revving its engine in front of the crowd that had spilled onto the street in Reno’s downtown. Several protesters confronted the driver and the passenger before the truck drives through the crowd, tires squealing, at about 6:40 p.m. Monday.

Soto said the activists did not have a permit to protest in the street, but some had gathered in the travel lanes of Virginia Street on the main casino drag.

Soto said he couldn’t comment on whether the driver or passenger felt threatened by the crowd and declined to comment on whether it was being treated as a hate crime.

“We are certainly looking into all aspects of the information that comes forward,” Soto told reporters.

“I want to make a point that we are going through a lot of video,” he said, describing some of it as “very horrifying.”

Quanah Brightman, executive director of San Francisco-based United Native Americans Inc., said the group was speaking out against the Dakota Access Pipeline in North Dakota when the truck approached.

“It was a hate crime,” she told the Reno Gazette-Journal.

One of the witnesses who posted video on Facebook Live said the two men in the pickup had been “stalking the protest” at the original site where the activists had gathered two blocks away.

“They drove by once as we were walking toward the arch, yelling obscenities,” said Taylor Wayman, 27, who said he was not an official member of the sponsoring groups but decided to attend the rally.

“I heard the driver ask one of the protesters, `Do you want me to kill your homies?’ and that really set everybody off,” Wayman told AP on Tuesday.

Reno Mayor Hillary Schieve said Tuesday she takes the matter “very seriously.”

“Public safety is our highest priority and I want all Reno residents to know that we are working swiftly and diligently to make sense of the events that took place last night,” she said Tuesday afternoon in a statement on behalf of herself and the city council.

“The Reno Police Department will hold anyone responsible accountable for their actions once the investigation has concluded,” Schieve said, adding that she respects an individual or group’s right to conduct lawful protest.

Soto said police dispatch received a 911 call about a vehicle striking pedestrians at 6:41 a.m. Officers arrived on the scene two minutes later and about a minute after that the pickup driver contacted police.

Mike Graham, founder of the Oklahoma-based United Native American Association, said Tuesday he doesn’t understand why the driver hasn’t been arrested.

“We are truly upset that he is not in custody. He left the scene of an accident,” Graham told The Associated Press.

The driver stopped several blocks away, and both he and a passenger in the pickup are cooperating, Soto said.

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AP Reporter Patrick Mairs in Philadelphia contributed to this report.