Deputies say Carlos Badillo, 29, and Juan Badillo, 23, got into an argument inside the family's home on Homebrook near Veterans Memorial around 9:30 p.m.
The father says the argument escalated and moved outside where Carlos grabbed a gun, shot Juan, then turned the gun on himself.
The father said he heard four shots, a pause, then another shot. He said Carlos was angry about something when he shot his younger brother.
One of the brothers died outside the house. The other brother was taken to a hospital where he died.
Deputies say the parents were inside the home when it all happened.
Investigators are trying to determine the cause of the argument.