Nov. 8 (UPI) -- Video of Sunday's service at the First Baptist Church of Sutherland Springs, Texas, shows the shooter methodically executing the victims, law enforcement officials said.
State and federal investigators reviewed gruesome footage from the shooting which showed Devin Patrick Kelley walking through the pews as he fired at the victims for about 7 minutes, the official told ABC News.
Kelley walked through every pew, crossing the main aisle several times as he quickly fired at the victims, which included small children, stopping only to reload.
The church regularly recorded its services to share online later.
Law enforcment agencies didn't say whether they would release the video which showed Kelley walking into the church armed with an assault rifle as well as magazines capable of holding more than 400 rounds of ammunition.
Kelley attended the church with his children for an annual fall festival five days before the assault, the Houston Chronicle reported.
Others at the event were surprised to see him because they knew Kelley -- who had been married twice and may have had issues with his mother-in-law, who attended the church --- had family troubles.
"And they thought, 'Oh, this is good. This is progress,'" Tambria Read, a longtime resident of Sutherland Springs who is close with Kelley's mother-in-law, told the Chronicle.
Read said that churchgoers would have helped Kelley through any difficulties he might have faced.
"This church is very loving, nonjudgmental and if he had had concerns or issues and spoken with the clergy - they're nonjudgmental," Read said. "They would have helped him deal with his issues and helped him try to get focused."
Kelley's life leading up to the attack was defined by arrests, accusations of harassment and sexual abuse and a string of odd jobs.
He was checked in to a mental health facility in New Mexico in 2012 after he attempted to bring firearms into an Air Force base to carry out death threats against the chain of command. In 2014, the Air Force discharged him with bad conduct after he served a year in prison for assaulting his wife and stepson.
Kelley was later charged with animal cruelty after neighbors saw him beating a husky in Colorado in 2014. The charge was dismissed about two years later.
Kelley killed 26 people, including an unborn child, and injured 20 others Sunday. A civilian shot Kelley twice before a car chase ensued. Police believe Kelley died from a self-inflicted gunshot wound.