At least four people were killed and “dozens” more were injured in a mass shooting in one of the most popular entertainment areas in Birmingham, Alabama, Saturday evening, the Birmingham Police Department said.

Just after 11 p.m., “multiple shooters fired multiple shots on a group of people” in the Five Points South area, Birmingham Police Officer Truman Fitzgerald said.

When officers arrived at the scene, they found two men and a woman unresponsive with gunshot wounds, and all three were later pronounced dead on the scene, Fitzgerald said. A fourth victim died at an area hospital, he added.

No suspects were in custody as of early Sunday, Fitzgerald said.

The incident extends the list of at least 403 mass shootings in the United States so far this year, according to the Gun Violence Archive. The archive, like CNN, defines a mass shooting as one in which at least four people are shot, excluding the shooter.

The victims in Alabama were all out in the open on the sidewalk or on the streets, Fitzgerald said. Detectives are working to determine whether the shooters walked up to the victims or drove by in a vehicle, he added.

Additional gunshot victims were identified in the area, and other victims arrived at local hospitals, Fitzgerald said. The University of Alabama at Birmingham Hospital received 11 of the victims, including one of the people who died, Hannah Echols, a hospital spokesperson told CNN. The conditions of the victims have not been released.

“We have dozens of gunshot victims from this area,” Fitzgerald said. “I’m told at least four of those gunshot victims are life-threatening, the others have various injuries.”

It’s unclear exactly how many people opened fire or what motivated the violence. Fitzgerald said police are investigating whether there were “multiple shootings.”

Several law enforcement agencies are assisting in the investigation, according to Fitzgerald. Birmingham police have asked that businesses in the area provide any surveillance footage they might have, and requested that the public reach out to them with any relevant information.

“Rest assured, we are going to do everything we possibly can to make sure that we uncover, identify and hunt down who was ever responsible for preying on our people,” he said.

Five Points South is a busy area known for its restaurants, night clubs, pubs and live music venues near the University of Alabama at Birmingham campus and a short drive from the downtown Birmingham area.

Fitzgerald said the mass shootings “have more to do with culture than they do criminality,” adding that “we’re seeing far too many arguments being settled by bullets.”