The man who led the high speed pursuit of the Texas gunman moments after he had killed 26 churchgoers, said "he needed to be stopped".

Johnnie Langendorff said he was driving in front of the First Baptist Church in Sutherland Springs when another man Stephen Willeford began trading rifle fire with the assailant.

Mr Willeford "jumped in my truck and said: 'He just shot up the church, we got to get him'," Mr Langendorff said. "I said: 'OK, let's go.'"

With Mr Willeford behind the wheel, Mr Langendorff said they "we blew through this intersection and he started going about 90-95 (miles per hour) keeping up with this guy."

Asked about what drove him to act so quickly, he added: "That's it. I mean that's the bottom line, he needed to be stopped. He was stopped and he's not going to hurt anyone else ever again."

At the time, neither man knew they were chasing 26-year-old Devin Kelley, an Air Force veteran who police say put on tactical gear, a ballistic vest and skull-like mask to carry out the most deadly mass shooting in the modern history of Texas.

The pursuit lasted about 10-12 minutes, according to Mr Langendorff. Then Kelley lost control and crashed into a ditch. They stopped too and Mr Willeford trained his rifle on the disabled vehicle, but the gunman never emerged.

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Mr Willeford shot Kelley where there was a gap in his vest, his cousin Ken Leonard told CNN.

"Stephen is the best shot that I know," he said. "He, without armour and barefooted ran into the fire and put his own life at risk, took return fire and fired accurately three times."

He added: "That's an amazing accomplishment, especially for a man who has, who was never in the military."