Stephen Willeford -- the man who chased and shot the man police believe killed 26 people in a Sutherland Springs church Sunday is sharing his story.

Willeford was at home when his daughter came into his bedroom to tell him she heard gunshots at the First Baptist Church nearby.

Willeford, a former NRA instructor, got his rifle out of his safe while his daughter looked outside again. She ran back in and told him she saw a man in black tactical gear shooting up the church.

"I kept hearing the shots, one after another, very rapid shots - just 'pop pop pop pop' and I knew every one of those shots represented someone, that it was aimed at someone, that they weren't just random shots," Willeford told ABC affiliate KHBS/KHOG.

Willeford loaded his magazine and ran across the street to the church, not even taking the time to put on shoes. When Willeford saw the gunman, he exchanged gunfire.

"He saw me and I saw him," Willeford said. "I was standing behind a pickup truck for cover."

"I know I hit him," Willeford said. "He got into his vehicle, and he fired another couple rounds through his side window. When the window dropped, I fired another round at him again."

The gunman then sped down the highway.

Willeford spotted a pickup truck at a stop sign. He ran to the truck and asked the driver for help.

"That guy just shot up the Baptist church. We need to stop him," Willeford told the driver.

Willeford and the driver chased the gunman down the highway. On the way, they called 911 to give a description of the gunman's vehicle and where they were.

Eventually, they caught up to the gunman's truck. The gunman slowed down before speeding up and hitting a road sign. The gunman's truck flipped and went down into a ditch.

Willeford got out of the truck and put his rifle on top of the truck, keeping his eye on where the gunman's vehicle was.

Willeford yelled "get out of the truck, get out of the truck," but never saw any movement. Law enforcement came to the scene. They believe the gunman committed suicide.

Willeford said he's no hero.

"I think my God, my Lord protected me and gave me the skills to do what needed to be done," Willeford said.

Willeford's family has lived in the Sutherland Springs area for four generations. He had numerous friends who went to the church.

The mass shooting left 20 others wounded in the small town, about 30 miles east of San Antonio.

Law enforcement later identified the suspect as Devin Patrick Kelley.

The massacre killed about 4 percent of the town's population. And no one at church was left unscathed, Wilson County Sheriff Joe Tackitt said.

"I think nearly everyone had some type of injury," the sheriff told reporters Monday.

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