Police in Dallas say four people are dead and 15 are injured following separate shootings in a Dallas neighborhood. It was among several violent incidents nationwide on Halloween weekend.

The police chief, Daniel Comeaux, said police are still trying to determine if the shootings in the Deep Ellum neighborhood were related.

Comeaux said three separate shootings occurred and it wasn’t immediately known why they started. Comeaux said some arrests were made but he didn’t specify how many or what charges were involved.

“This is a really big scene. It’s spread out,” Comeaux said. “We are interviewing some individuals right now that we have arrested, still trying to figure out exactly how it ties into all the shootings out here.”

A police statement said the shootings occurred over a span of one hour and 15 minutes. No police officers were injured. The Deep Ellum neighborhood is in an entertainment district filled with a variety of shops and restaurants.

It was among several violent incidents nationwide on Halloween weekend.

Separately, one person was killed and eight others were wounded in a mass shooting just outside Legion Field in Birmingham, Alabama, after the annual “Magic City Classic” football game on Saturday night, police said.

In Newark, Delaware, six people were shot shortly late Saturday near the University of Delaware campus, Newark police Lt Greg D’Elia said. All six were transported to hospitals for treatment. Video shared on social media showed people running for safety from the scene. One stretch of the city’s Main Street was closed for several hours after the shooting.

A shooting early Sunday in Bloomington, Illinois, left a 19-year-old woman dead and another woman in critical condition. Six others had injuries that were not life-threatening, but it was unclear from a statement by the city’s police department and McLean county coroner’s office if those people had gunshot wounds. The shooting happened near the campus of Illinois Wesleyan University. Bloomington is about 135 miles (217km) south-west of Chicago.

And in Fayetteville, Arkansas, six people were taken to hospitals with gunshot wounds from a shooting that happened early Sunday. No arrests have been made, police said in a news release. A preliminary investigation indicates an altercation preceded the shooting.