An off-duty Texas police officer shot his own son on Saturday night after he mistook him for an intruder, authorities said.

The "long-term veteran" officer of the Dallas Police Department arrived at his home in DeSoto on Saturday around 6 p.m. and thought a trespasser was inside.

The "intruder" was his adult son, according to Pete Schulte, a spokesperson for DeSoto police. The police officer called 911 and identified himself as an off-duty Dallas cop.

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Investigators arrived to find the son, identified as in his 20s, as"lightly struck by a bullet in his arm." The officer told authorities he mistook his son for an intruder, Schulte said.

"It was a mistake. He thought that there might have been an intruder in the house. He didn't know who was supposed to be there and so forth," Schulte said. "It was a startling situation, it was an accident."

The spokesman said the shooting happened in the garage area of the property. He said the officer got home and noticed "the house was not in the state that he had left it" — the garage door was open, and "some doors were locked that weren't locked" when he left earlier in the day.

"He thought that maybe something had happened inside and, of course, we did ask the question, 'Why didn't you call us, the DeSoto Police Department?' and like most people say is like, 'I just wanted to know what was going on before I wasted a call to 911,'" Schulte said the off-duty officer told police.

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Authorities, the spokesperson said, want people to know "that if you come home and something doesn't feel right, [it] doesn't bother us at all, go ahead and call 911, so we can come out and check it out ."

Schulte said the off-duty officer's version of events is consistent with evidence at his home, and that no charges have been filed at this time.

Neither the father nor son were identified.