Source Says Texas Shooter 'Was There to Kill Everybody'

Texas church shooting suspect Devin Kelley planned to "kill everybody" at the First Baptist Church in Sutherland Springs, Texas on Sunday, a source said.

"He was there to kill everybody. He is a mass killer of children and people ... he is a horrible monster," a source "familiar with the matter" told ABC News Monday.

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Texas officials are still investigating the worst mass shooting in the state's history. Twenty-six people were killed, and 20 others injured in the shooting. A resident was credited with stopping Kelley and following him out of the church. He was found deceased in his vehicle in nearby Guadelupe County.

Authorities said at a news conference Monday that there was a "domestic situation" within Kelley's family and the shooting was not racially or religiously motivated. They said his mother-in-law attended the church. He sent "threatening texts" to her and "expressed anger towards her," authorities said.

"I don't think this was just a random act of violence," Texas Governor Greg Abbott said Monday. "It was two things: one is, a very deranged individual, who I understand, long before he was dishonorably discharged from the United States military was demonstrating some mental illness challenges. But also, there, I think, was a particular reason why this particular location was targeted."

"He came there to kill everybody in that building. Period," a source told ABC News.

Authorities said they reviewed video of the service during the shooting. The church posted videos of Sunday services on YouTube every week.

The victims of the shooting ranged in age from 18 months to 77 years old. Half of the 20 people injured remained in critical condition at local hospitals, while four are in serious condition and six are in stable condition or have already been released.

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Sutherland Springs is located in Wilson County, about 35 miles southeast of San Antonio. The town has a population of 362, so about 7 percent of its population was killed in the shooting.

Photo credit: Getty