Texas shooter Devin Patrick Kelley
Texas shooter Devin Patrick KelleyReuters

The gunman who murdered 26 people in a mass shooting in a Texas church Sunday was a social outcast who "preached" atheism, the Daily Mail reported.

Authorities said that Devin Patrick Kelley opened fire at congregants gathered inside the First Baptist Church in Sutherland Springs at approximately 11:30 a.m., half an hour after Sunday church services began.

Friends and acquaintances of Kelley told the Daily Mail that he was "creepy" and "weird."

"He was the first atheist I met. He went Air Force after high school, got discharged but I don't know why," said Patrick Boyce, who attended high school with Kelley.

"I was just shocked [to hear the news]. Still haven’t quite processed how he could have done that," Boyce added.

Nina Rose Nava, another former classmate of Kelley, wrote on Facebook that she had unfriended Kelley because of his rants against religious people. "In complete shock! I legit just deleted him off my fb cause I couldn't stand his post."

"He was always talking about how people who believe in God we're stupid and trying to preach his atheism," she added.

Another classmate told the Daily Mail, "I grew up going to school with him... Always creeped me out and was different."