Officials still don't know how the Texas shooting suspect died

Darren Abate/AP

Law enforcement officers man a barricade near the First Baptist Church of Sutherland Springs after a fatal shooting, Sunday, Nov. 5, 2017, in Sutherland Springs, Texas.

• The suspect behind the deadliest shooting in the history of Texas died Sunday following a police chase.
• The circumstances of Devin Patrick Kelley's death remain unclear.
• It's possible that he killed himself or was shot by a local resident who confronted him.

Devin Patrick Kelley, the man identified as the suspect who shot at least 26 people at First Baptist Church in rural Texas on Sunday, died after a brief police chase. The cause of his death, however, is still unknown.

Authorities have been trying to piece together the timeline of the Texas shooting, which Gov. Greg Abbott called the deadliest in the state's history, since Kelley allegedly opened fire on Sunday morning during services.

Details about the victims, how exactly the massacre unfolded, and Kelley's motive are just beginning to emerge.

The circumstances of the gunman's death, however, remain unclear.

According to Freeman Martin, the regional director for the Texas Department of Public Safety, Kelley parked his car at a gas station across the street from the church at about 11:20 a.m.

Kelley then crossed the street, exited his car, and began shooting at the church from the outside with a Ruger military-style rifle. He continued shooting as he moved to the right side of the church, eventually entering the building.

Once Kelley exited the church, Martin said, Kelley was "engaged" by a rifle-wielding resident who lives next-door to the church. At that point, Kelley dropped his weapon and sped away in his vehicle while the resident followed.

After a brief chase, deputies found Kelley dead in his car off the side of the road in neighboring Guadalupe County. Authorities said they don't know whether Kelley killed himself or was killed by the resident who pursued him. Kelley was wearing all black "tactical-type gear" and a bulletproof vest, Freeman said.

Wilson County Sheriff Joe Tackitt speculated Monday morning that Kelley shot himself.

"At this time we believe that he had a self-inflicted gunshot wound, after he wrecked out," he told CBS News.