(CNN/KGTV) - The victims in Sunday's mass shooting at a Texas church ranged in age from 18 months to 77 years, officials said.
Law enforcement officials Monday confirmed 26-year-old Devin Kelley carried out the shooting at the First Baptist Church in Sutherland Springs that killed at least 26 people and injured 20 others.
Officials said Kelley, wearing all black clothing with a black mask and a ballistic vest, entered the church and opened fire. Following the rampage, officials said Kelley was confronted by a nearby resident who responded to the gunfire.
RELATED: At least 26 dead, 20 injured after gunman opens fire at Texas church
The resident was armed with a rifle, and officials said Kelley and the resident exchanged gunfire before Kelley dropped his weapon and fled the scene in a Ford Explorer SUV. The resident flagged down another man and both men pursued the gunman in a truck and contacted authorities.
Kelley, according to officials, called his father and told him he was shot and "may not make it." Kelley's SUV eventually crashed in a ditch.
Officials said Kelley was found dead in the SUV. While the cause of his death remains under investigation, officials said evidence at the scene indicated he may have died from a self-inflicted gunshot wound.
An FBI official noted Kelley did not have any known ties to terrorist groups.
RELATED: Who is Devin Kelley, Texas church mass shooting suspect?
The shooting was not believed to be racially or religiously motivated, and officials said the incident may be linked to a domestic situation involving the shooter and his family.
One official said Kelley sent threatening text messages to his mother-in-law, who had attended the church in the past but was not there when the shooting occurred.
Officials said three weapons -- a rifle and two handguns -- were recovered by investigators. They were all purchased by Kelley, officials confirmed.
Kelley did not have a license to carry, officials said. It was noted that Kelley had a private security license similar to those who work as security guards at concerts.
Investigators are reviewing video that was recorded at the church.
Resident confronted gunman after shooting
After the gunman opened fire at the First Baptist Church in Sutherland Springs, killing at least 26, he left the church but was confronted by an armed resident, CNN reported.
Following a shootout, witness Johnnie Langendorff told CNN affiliate KSAT the gunman drove away in a Ford Explorer. Langendorff said the resident "briefed me quickly on what had just happened and said we had to get him, and so that's what I did."
They gave chase in his truck and called police. As they sped after him, Langendorff said, the shooter "eventually lost control on his own and went off into the ditch" in neighboring Guadalupe County.
"The gentleman that was with me got out and rested his rifle on my hood and kept it aimed at him [shooter], telling him to get out. There was no movement, there was none of that. I just know his brake lights were going on and off, so he might've been unconscious from the crash or something like that. I'm not sure."
Law enforcement later found the suspect dead of a gunshot wound inside his vehicle.
Sheriff: Gunman's ex-in-laws attended same church "from time to time"
The former in-laws of a man suspected of opening fire and killing at least 26 people at a Texas church Sunday attended services at the church on occasion.
In an interview with CNN, Wilson County Sheriff Joe D. Tackitt Jr. said the shooter's former in-laws attended mass at the First Baptist Church in Sutherland Springs "from time to time," but they were not there when the shooting occurred.
The gunman, identified by Texas authorities as 26-year-old Devin Kelley, served in the Air Force but received a bad conduct discharge in 2012 for assaulting his spouse and their child.
Other developments, according to CNN reports:
-- Ten people remain in critical condition Monday, authorities said. A total of 20 people were wounded. And virtually no one at the church was left unscathed, Tackitt said. "I think nearly everyone had some type of injury," the sheriff told reporters Monday.
-- The 14-year-old daughter of the church's pastor was among those killed, said Sherri Pomeroy, the girl's mother. Her parents were traveling out of state when the shooting occurred.
-- At least eight of the people killed were members of one family, according to a relative and a community leader. A woman who was about five months pregnant and three of her children were killed. The pregnant woman's brother-in-law and his young child were also killed, according to the community leader. Three other members of the same family were wounded. CNN is not naming the victims at this time, as it isn't yet confirmed that their next-of-kin have been notified.
-- Speaking from Japan, President Donald Trump expressed condolences for the victims during a Monday news conference and said he believes the shooting was caused by a "mental health problem," not an issue with U.S. gun laws.
