David Conley was charged with capital murder after deputies discovered the bodies of two adults and six children in their Houston-area home early Sunday.
Conley, 48, forcibly entered the home because the owners had changed their locks, authorities said.
His motive appears to be related to the mother of the children, who had a past relationship with him, Harris County Sheriff's Chief Deputy Tim Cannon said.
One -- and possibly two -- of the children killed might have been the suspect's, authorities said.
"Once again, a senseless tragedy has struck our community," Cannon said. "Our hearts go out to the family and friends of those lost."
Call for a welfare check
Late Saturday night a relative called authorities and asked them to perform a welfare check on the residence.
When deputies arrived at the scene, they knocked on the door, but no one showed up, said Thomas Gilliland, a spokesman for the sheriff's office.
Deputies surrounding the house saw a child's body through the window and entered the house.
The suspect allegedly fired at them, forcing them to pull back and wait for hostage negotiators and a unit that specializes in high-risk situations.
Hours of standoff
After hours of negotiations, authorities said they coaxed the suspect into coming out and arrested him.
They found a gruesome scene in the three-bedroom house.
"Upon entering into the home ... to check for the welfare for any other people in the house, the bodies of eight victims were found inside the residence," Gilliland said.
The victims were spread out in all bedrooms, shot to death, some multiple times, authorities said.
The victims' ages ranged from 6 to 50 and included a woman, her husband and six children, according to Cannon.
They are Valerie Jackson, 40, and Dwayne Jackson, 50. The children are Nathaniel, 13; Honesty, 11; Dwayne, 10; Caleb, 9; Trinity, 7; and Jonah, 6.
The spokesman said authorities have been called to the house before, but the nature of those calls was not immediately available.
Conley has been charged with three counts of capital murder. Authorities said in such cases, one capital murder count includes multiple deaths.
He is being held in the Harris County Jail without bail.