Less than 24 hours after police say a man shot four relatives before turning the gun on himself, grief counselors were sent Wednesday to a Gwinnett County middle school attended by one of the victims.

Police have not said what caused 30-year-old Brandon Mclean to shoot his mother, aunt, niece and nephew.

A witness called 911 Tuesday after hearing gunshots, Gwinnett police Cpl. Jake Smith said, and at an apartment in the 6000 block of Bannor Lane in Peachtree Corners, they found 13-year-old Kayla Serrano and 19-year-old Andre Mclean dead at the scene.

Serrano was a student at Pinckneyville Middle School, where additional counselors were on hand Wednesday, Gwinnett schools spokeswoman Sloan Roach told The Atlanta Journal-Constitution. Andre Mclean attended high school at a county school last year, Roach said.

Serrano was the niece of Brandon Mclean, Smith said. Andre Mclean was his nephew. Police believe Brandon Mclean used a handgun to shoot the teenagers as well as two other relatives – his mother, 57-year-old Betty Mclean, and her sister, 52-year-old Charlotte Longnecker. Betty Mclean was the grandmother of the deceased teenagers. The women were taken to Gwinnett Medical Center and were reported to be in serious but stable condition, Smith said.

Following the shootings, Smith said, Brandon Mclean was taken from the scene with an apparent self-inflicted gunshot wound and died at the hospital.

“Detectives are convinced at this point that we’re not looking for any additional suspects, and they’re also convinced at this point that [Brandon Mclean] was the shooter and that his own injury was self-inflicted,” Smith said.

Investigators have not found thus far any prior incidents of violence in Brandon Mclean’s history, Smith said, adding that they would continue to delve into the man’s past as the investigation continues.

Police continue to speak to friends and family, but are not ready to announce a motive in the case.

“We believe it was domestic-related,” Smith said. “We don’t think this stemmed from a robbery or anything along those lines. We know that Brandon had been in and out of the home prior to the shooting. We do believe he had been staying here before the shooting. The exact circumstances that led up to the shooting, we can’t say precisely at this point, but we’re still fairly early in the investigation.”

—Staff writers Mike Morris and Alexis Stevens contributed to this report.