Cameron Gerald Dorsey, 20, was arrested Sunday morning near his family's southeast Houston church.
Investigators believe he murdered his great grandfather, Pastor Clements Vincent Dorsey Sr., 89, and his 61-year-old great aunt, Barbara Dorsey Alexander.
Both victims were found beaten to death in the kitchen of the pastor's home Thursday after firefighters extinguished a blaze there. Prosecutors allege Cameron Dorsey beat the pair to death with a sledgehammer.
A third person in the house -- the pastor's wife -- slept through the entire ordeal.
Cameron Dorsey was allegedly seen leaving their home shortly after the murders.
Police say Cameron Dorsey was recently released from jail and had moved in with his grandfather. However, he was asked to move out right before the slayings. He has a criminal history of theft against the elderly.
Cameron Dorsey was caught Sunday at Broadway and Highway 225. He was walking away from his family's church off Gibbons.
The church wasn't open Sunday, but the actions of observant neighbors led police to take the grandson into custody.
"He went right down by the warehouse right here," witness Jack Howitt said. "He came back up and got on the porch and I said, 'Go ahead and call police, that's him. Please hurry and call police.'"
"I wasn't nervous at all because I knew him when he was a little boy and I knew he wouldn't come over here and mess with us," the woman who called 911 told us.
Police say Dorsey did not resist arrest. Family members were on the scene once he was in the police car. They were visibly upset and still grieving over their loss.
The suspect is expected in court Tuesday. No bond was set.
Stay with Eyewitness News and abc13.com for updates as we continue following this story.