The Texas gunman who stormed into First Baptist Church on Sunday -- killing 26 people, including an 18-month-old -- had previously threatened his mother-in-law, who frequented the church but was not in the pews on Sunday, officials said.
Texas Department of Public Safety Regional Director Freeman Martin said "there was a domestic situation" within gunman Devin Patrick Kelley's family, and he threatened his mother-in-law in text messages.
"The suspect's mother-in-law attended this church," Martin told reporters.
Martin added the massacre was not believed to be racially or religiously motivated.
Kelley was dressed entirely in black during Sunday's attack and also wore a face mask replete with a white skull, Martin said.
"He was obviously suspicious to others based on how he was dressed in all black," he said. "He was wearing a face mask with a white skull on it."
After his rampage at the church, Kelley engaged in a shoot-out with a neighbor who engaged the gunman.
“A local resident who lives across the street from the church heard what was going on,” Martin said.
Kelley was hit at least once in the shoot-out, and jumped into an SUV to flee the scene, followed by 2 Good Samaritans.
During the pursuit, Martin said the 26-year-old called his father to tell him he was shot, and "didnt think he was going to make it."
Officials believe Kelley died of a self-inflicted gunshot wound after he crashed his car.
Of the 26 killed in the rampage, 23 people were found dead inside the church, two outside the building and one later died at the hospital, according to Martin. The victims ranged in age from 18 months to 77 years old, and one of those who died was pregnant.
A total of 20 people were were injured in the shooting, 10 of which are still hospitalized in critical condition. Those treated in hospitals ranged in age from 5 to 73, according to Martin.