Dozens of people were injured and at least six people died in mass shootings as gun violence broke out at nightlife districts in half a dozen cities across the country over the Halloween weekend.

Police in Dallas, the site of the deadliest violence, said four people are dead and 15 others were injured following a handful of shootings in the city's Deep Ellum neighborhood, a center of music, restaurants and nightlife in the city. Police in college towns like Fayetteville, Arkansas; Birmingham, Alabama; and Newark, Delaware, also reported shootings in their nightlife districts this weekend.

Dallas Police Chief Daniel Comeaux said investigators are still trying to determine if the shootings Saturday night over the span of about an hour and 15 minutes 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.…