NEWBERRY, S.C. (AP) — Four teenagers were shot dead within hours of each other in a small South Carolina city over the weekend, prompting the area high school to switch to virtual learning while officers stepped up patrols, authorities said.

No arrests have been made in the shootings early Sunday in Newberry that killed a 16-year-old and in the deaths of three teens in a shooting that afternoon about two blocks away in the city of 10,200 people, Newberry Police Chief Kevin Goodman said.

“All the victims are somehow connected,” Goodman said. “They knew each other. My understanding they were in the same circle.”

The victims in the second shooting ranged in age from 15 to 19, Newberry County Coroner Laura Kneece said. She has not released the names of the victims and said autopsies are planned.

One of the people questioned in the first shooting was killed in the second shooting. Goodman said it is too early to determine if retaliation was involved and that he hoped to release more information Monday.

“When you really don’t know all the players and what it is stemming from, that’s always a concern,” Goodman said.

Newberry police were patrolling throughout the city about 40 miles northwest of Columbia with help from Newberry County deputies and state police.

Newberry High School decided to make Monday an e-learning day, closing campus as a precaution even though no direct threat had been made.