Authorities named 26-year-old Devin Kelley as the gunman in Sunday’s devastating Texas church shooting that left at least 26 people dead and even more injured. Investigators said they had not yet determined Kelley’s motive but were looking into his social media activity to glean information.

Though authorities were still investigating, Kelley did not appear to be linked to any organized terrorist groups, an official with knowledge of the matter told the Associated Press. One of his social media posts in the days leading up to the attack may have depicted an AR-15 semiautomatic weapon, the official also noted. The FBI and Bureau of Alcohol, Tobacco, Firearms and Explosives were both deployed to assist in the investigation into the shooting.

Kelley apparently wore all black tactical gear and a ballistic vest when he opened fire on the crowd of worshippers Sunday afternoon, leading some authorities to believe the attack was planned well in advance. The gunman had no connection to the church and was not from the town, Sheriff Joe Tackett told CNN. He was reportedly a former United States Air Force member who was dishonorably discharged, CBS News reported. 

Kelley himself died after a brief chase into a neighboring county. It remained unclear whether he died as a result of a self-inflicted gunshot wound or if he was shot by a resident who exchanged fire with him.

The massacre was the worst mass shooting in Texas history, Gov. Greg Abbott said in a press conference. Authorities said Sunday evening they were not ready to share the names of victims until family members could be notified but said the ages of those killed or injured ranged from 5 to 72 years old.

President Donald Trump condemned the shooting as “horrific” during a speech from Tokyo.

“Victims and their families were in their sacred place of worship,” Trump said. “We cannot put into words the pain and grief we all feel. In dark times such as these, Americans do what we do best and we pull together. We lock hands and we join arms. Through the tears and through the sadness we stand strong."