A Houston man was taken into custody early Sunday morning after he flagged down an officer and reported that he had just assaulted his stepfather.

Accompanied by his mother, the man said he attacked his stepfather in self-defense after he approached him with a knife, KTRK reported.

Police went to the apartment, about a mile away, and forced their way inside, where they found the 71-year-old man dead.

“We don’t really know why this happened this morning. There’s no one else in the house besides the elderly man,” Houston Police Sgt. Michael Cass said. “There is a large scene behind me here; broken furniture. You can really see that something violent took place, but the man was so old I don’t know how this would have happened.”

Cass said the stepson is cooperating with the investigation.

“It’s really sad that we see this, especially on Father’s Day,” he said.

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