By Madison Park, Dakin Andone and Kaylee Hartung, CNN

(CNN) -- [Breaking news update at 7:43 a.m. ET]

The gunman in Sunday's church mass shooting had in-laws who attended the church -- but those in-laws were not present at the time of the massacre, Wilson County Sheriff Joe Tackitt told reporters.

The in-laws came to the church after hearing about the shooting Sunday. The attack in Sutherland Springs left 26 people dead, including the visiting pastor, Tackitt said.

"I think nearly everyone had some type of injury," the sheriff said.

[Previous story, published at 6:52 a.m. ET]

At least eight members of the same family were among the 26 people killed Sunday when a man armed with a rifle burst into the sanctuary of a church in Texas and began firing.

The massacre left about 20 others wounded in the small town of Sutherland Springs, located about 30 miles east of San Antonio.

Texas Gov. Greg Abbott called the slaughter "the largest mass shooting" in the state's history and ordered flags across the state to fly at half-staff Monday.

Latest developments

-- The victims ranged in age from 5 to 72 years old, said Freeman Martin, a regional director with the Texas Department of Public Safety.

-- 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.

-- 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.

--The gunman was dressed in all-black tactical gear, including a ballistic vest, Martin said. He fled the church and was later found dead in his vehicle, officials said.

-- Authorities said an armed resident confronted the gunman outside the church and shot him.

-- A witness told CNN affiliate KSAT that he and the armed resident pursued the gunman in a car chase for roughly 11 miles.

-- 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 US gun laws.

Who is the shooter?

The gunman has been identified as 26-year-old Devin Patrick Kelley, according to two law enforcement sources who have been briefed on the investigation.

But police have not officially named Kelley as the shooter. They described the gunman as a white man in his 20s. Authorities have not said what the motive was.

Kelley was a member of the US Air Force and served at Holloman Air Force Base in New Mexico from 2010 until his discharge, according to Air Force spokeswoman Ann Stefanek.

He was court-martialed in 2012 for assault on his spouse and assault on their child, according to Stefanek. He served a year in confinement, received a bad conduct discharge and had his rank reduced, she said.

In April 2016, Kelley purchased the Ruger AR-556 rifle he allegedly used in the shooting from a store in San Antonio, Texas, a law enforcement official said. There was no disqualifying information in the background check conducted as required for the purchase, a law enforcement official told CNN.

How the attack unfolded

The gunman was first spotted at a Valero gas station across the street from the church at about 11:20 a.m. (12:20 p.m. ET).

He drove his vehicle across the street, got out and began firing before he entered the church, Martin said during Sunday's news conference.

David Flores told CNN that his father saw the shooter.

"My dad saw the gunman run into the church building and then he heard shots and saw people running," Flores told CNN. "People covered in blood and screaming. It was pandemonium everywhere."

As the shooter left the church, a local resident used his own rifle to engage him, Martin said. The gunman dropped his weapon and fled.

Johnnie Langendorff said he was driving to his girlfriend's house when he saw the exchange of gunfire between the shooter and the armed resident.

The gunman took off in a Ford Explorer, Langendorff told CNN affiliate KSAT.

Local coverage from KSAT

The resident "briefed me quickly on what had just happened and said we had to get him, and so that's what I did," Langendorff said.

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.

"At this time, we don't know if it was a self-inflicted gunshot wound or if he was shot by the local resident," Martin said.

A law enforcement official briefed on the investigation said multiple weapons were found in the shooter's car. The FBI and the Bureau of Alcohol, Tobacco, Firearms and Explosives are involved in the investigation.

Community grieves

Hours after the shooting, residents of Sutherland Springs hugged one another, held candles and sang hymns in a vigil Sunday night. Abbott attended the event, in which faith leaders offered words of solace and prayers.

Sutherland Springs is the kind of place where "everybody knows everybody," said Gloria Rodriguez Ximenez, who attended the vigil.

"This is a small, Christian town, a very small community," she said. "Everybody's united. Everybody's so close to everybody."

She knows the First Baptist Church's pastor and his family, including their daughter who died.

"I can feel the pain everybody's going through. There's so much hurt for a small town," Ximenez said.

Others echoed the feeling of shock and heartache.

"My heart is broken," Wilson County Commissioner Albert Gamez Jr. told CNN. "We never think where it can happen, and it does happen. It doesn't matter where you're at. In a small community, real quiet and everything, and look at this."

Local coverage from KABB

Twenty-three people died inside the church, which has a small sanctuary with wooden pews and red carpeting. Two died outside the church and one at the hospital.

"We don't know names of any of the victims at this time," said Wilson County Sheriff Joe Tackitt in a news conference Sunday evening. As victims are identified, next of kin will be notified, he said.

The wounded are being treated at three hospitals including the Connally Memorial Medical Center in Floresville, University Hospital and Brooke Army Medical Center in San Antonio.