The black-clad gunman who massacred 26 people in a Texas church walked up an down the aisle shooting people as they lay on the floor to escape the rampage, the son of a survivor told CNN on Monday.

David Brown, whose mother is recovering from leg wounds she sustained during the Sunday massacre at the First Baptist Church in Sutherland Springs, Texas, described to CNN’s "OutFront" the chilling chain of events as gunman Devin Kelley, dressed in black, sprayed the congregation, killing 26 men, women, and children.

"After people stopped running out of the church, he started walking around," Brown told CNN. "He walked up and down the aisle shooting everyone that was laying on the ground. He walked up and down the aisles a few times, and made his way around the church, and eventually ended up where she was, which is in the very back pew and started shooting the lady next to her, multiple times.

"She was pretty certain she was next and her life was about to end. Then someone with a gun showed up at the front of the church, caught his attention, and that was the end of it."

Brown said the rampage started when "out of nowhere, shots starting coming through the windows."

"Then the shooter came in through the front doors, and the Sunday schoolteacher sitting next to her yelled, 'get on the floor,'" he said. "She got on the floor. A lady sitting to her left also got on the floor . . . the shooter came into the church and started shooting everyone. And people were running out of the church. And she thinks he was shooting them as they were leaving."

Brown said his mother is devastated by the shootings.

"She said she would have taken 15 more shots to the legs if it would have saved lives," he said. "She's more heartbroken about all the lives that were taken and the helpless defenseless church members that just laid there and met their end . . ."

"She knows how fortunate she was to live through this," he added.