Police in Boulder, Colo., said Sunday that several people were injured and a suspect is in custody following reports that someone was setting people on fire at an outdoor mall.

Although the FBI immediately described the incident as a "targeted terror attack," Boulder police Chief Steve Redfearn said it was too early to discuss a motive, but that witnesses were being interviewed.

"It would be irresponsible for me to speculate on motive this early on," he said.

The Boulder attack took place at a popular pedestrian mall known for attracting tourists and college students.

On Sunday, demonstrators with a volunteer group called Run for Their Lives had gathered to call for the release of hostages who remain in Gaza. The group has multiple chapters across the world that regularly meet to walk to advocate for hostage releases.

Boulder police said there were "several victims" in the attack. The injuries authorities found were consistent with reports of individuals being set on fire, Redfearn said, adding that injuries ranged from serious to minor.

Multiple blocks of the pedestrian mall area were evacuated by police. The scene shortly after the attack was tense, as law enforcement agents with a police dog walked through the streets looking for threats and instructed the public to stay clear of the pedestrian mall.