A 14-year-old boy allegedly shot and killed three teenagers and left a fourth critically wounded at a Texas gas station on Sunday night, police said Monday.

The shooting occurred in Garland, a suburb of Dallas, at a Texaco convenience store in the 700 block of Walnut Street, KDFW Fox 4 News reported.

Garland Police Chief Jeff Bryan said a 14-year-old boy believed to be the shooter was arrested at 4 p.m. Monday, according to The Dallas Morning News. Bryan didn't release any details regarding where and how the boy was arrested, only saying that he didn't turn himself in.

"We're trying to complete an accurate and thorough investigation and arrest," Bryan was quoted by The Dallas Morning News. "We owe that to the families."

Authorities have yet to name the suspected shooter, who was seen wearing a blue surgical mask, baseball hat and dark-colored athletic shorts in surveillance footage.

Investigators also have yet to determine a motive or what led to the shooting, The Dallas Morning News added.

Police showed surveillance footage during a news conference where a shirtless boy or man could be seen crouching while walking toward the store with a handgun. He opens the door and, from the doorway, begins to shoot into the store.

The man fired over 20 rounds from a .40-caliber pistol, police said.

Police said the suspected shooter then got into a white Dodge Ram pickup with a scrape on the passenger side and that someone else drove him away. Authorities are still looking for the driver of the pickup.

Emergency Response
A 14-year-old boy allegedly shot and killed three teenagers and left a fourth critically wounded at a Garland, Texas, gas station on Sunday night, police said on Monday. Above, police vehicles respond to a crime scene.Getty Images/Matt Gush

Two of the victims who died were 16-year-old boys who had arrived at the store together. The third who died was a 14-year-old boy who was there ordering food from the kitchen.

The fourth person who was shot and critically wounded was the cook at the store. He is 15 and was still hospitalized on Monday.

Their names have not yet been released.

Bryan said the young ages of the victims and the suspected shooter make this difficult for him and his officers to investigate on a personal level.

"I have kids about the same age, and to comprehend the day after Christmas—when most people are winding down through the holidays and getting ready to go back to school—and now we're trying to support and help families through this," Bryan said. "It's difficult to describe in a lot of ways, but we know we have a job to do."

The Associated Press contributed to this report.