Investigators hold a Monday morning news conference in Sutherland Springs, Texas on Nov. 6. (Screen grab/Fox News)

(CNSNews.com) - Authorities in Texas said the mass shooting at the First Baptist Church of Sutherland Springs, Texas, was not random.

"There was a domestic situation going on within this family," authorities said at Monday morning news conference. They said the suspect had sent threatening texts to his mother-in-law, who occasionally attended the church.

Authorities refused to go into detail about the domestic situation, except to say the guman was angry at his mother-in-law.

They also said he wore a mask with a skull on it while walking among the pews, killing 26 people and wounding 20 others.

The 26-year-old gunman, who reportedly was dishonorably discharged from the Air Force in 2014 following a conviction for assaulting his wife and child, did not have a license to carry a gun, authorities said.

"The suspect did have a noncommissioned, unarmed private security license, similar to a security guard at a concert-type situation,” said Texas Department of Public Safety Regional Director Freeman Martin. “There were no disqualifiers entered into the National Crime Information Center database that would preclude him from receiving a private security license.

“Private security background checks including fingerprints and criminal history checks with the Texas Crime Information Center and the National Crime Information Center databases were checked and he was cleared,” Martin added.

The National Crime Information Center is one of the databases accessed by the National Instant Criminal Background Check System, which is supposed to bar domestic abusers and dishonorably discharged veterans from legally buying guns.

Authorities said the gunman bought four weapons in total, two in Colorado, and two in Texas, one each year beginning in 2014.

An ATF official said three of the four guns have been recovered, including the semi-automatic rifle he dropped at the scene when he was shot by a good Samaritan as well as two pistols found later in his car.

The ATF official said in general, if an individual has a dishonorable discharge from the military, he would be prohibited from possessing firearms. The investigation is continuing into exactly what the gunman's discharge said and whether this is a case of someone slipping through the cracks of the background check system.

In another detail, authorities said the suspect called his father while two bystanders were pursuing his SUV "to notify his father that he had been shot and didn't think he was going to make it."

Authorities say it appears he shot himself when his vehicle crashed.