The daughter of a man killed in a church shooting on Sunday as he served communion has said she forgives her father's killer. 

Tiffany Wallace told NBC News affiliate KXAS that her father, Anton "Tony" Wallace, was serving communion when a gunman entered into West Freeway Church in White Settlement, Texas, and opened fire. 

She was attending the service with her children at the time of the shooting, in which her father and one other man died. 

The gunman has been identified as Keith Thomas Kinnunen, 43, who was killed at the scene by armed members of the congregation. 

Recounting the terrifying moment when the gunman opened fire, Wallace told KXAS: "It just happened so fast and it was so crazy.

"I was like, 'not my dad, not my dad.'"

After ensuring her own children were unharmed, she rushed to her father's side to tell him she loved him.  He died shortly after from his injuries in hospital. 

She told KXAS that her father, a registered nurse, was a "godly" man who was popular at the hospital where he worked as well as in the church, where he was a deacon.

"He was just our rock that held us together," she said.

"Even when talking about Heaven, he said he was always prepared, but I never thought this would happen. You think dad would get old and sick but never get murdered."

Wallace said that she had noticed the gunman in the pews and had planned to go over to greet him, thinking that he was a newcomer looking for a new church home.

If he had "needed food shelter, we would give it to him — whatever he needed", she said, adding, "He didn't need to take an innocent life, our dad, grandfather, husband."

She admitted that forgiving the gunman was not easy. 

"How could someone so evil, the devil, step in the church and do this?" she said. 

"I forgive him, and it's the hardest thing to say because it's like, somebody killed your dad, but I forgive him," she said, although she added, "I'll never forgive what he did, but I forgive him."

Texas Lt Gov Dan Patrick praised the church's security team for preventing more deaths in the tragedy.

"This church had its own security team. They were well-trained," he told reporters. "The heroism today is unparalleled. This team responded quickly and within six seconds, the shooting was over."