Texas church gunman Devin Patrick Kelley had three guns and had been involved in a domestic row with his mother-in-law, officials have said.
The attack on the small church outside of San Antonio during Sunday services left 26 people dead and 20 injured.
The gunman called his father after he was shot by an armed bystander, and said he did not think he would survive.
Kelley was not legally permitted to own the weapons, which included an assault rifle and two handguns, police said.
Investigators said on Monday that the suspect dropped an assault rifle in the church before fleeing the scene.
Freeman Martin, the regional director for the Texas Department of Public Safety, told reporters it appeared that Kelley died from a self-inflicted gunshot wound after first being shot by a “Good Samaritan”.
Officials have not yet identified the victims.