A Florida man is accused of fatally shooting his ex-wife and her son Sunday in an argument about electricity usage, authorities said.

Michael Williams, 47, became enraged after finding out that Marsha Ebanks-Williams, 48, and her son, Robert Adams, 28, had clipped a lock he had installed on the electrical box to prevent them from racking up a high electricity bill, according to the Volusia County Sheriff's Office.

"Michael was upset that he felt that they were leaving the lights on in the house, and he went and put a lock on the box outside the house, which Marsha and her son cut," Chief Deputy Brian Henderson said Monday at a press conference. 

"So he became upset, and that started this argument which ultimately resulted in these two people getting shot and killed."

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Brian Henderson holds up a booking photo of Michael Williams at a press conference.

Volusia Sheriff's Office Chief Deputy Brian Henderson at a press conference Monday announcing murder charges against Michael Williams, who is accused of fatally shooting his ex-wife and her son over electricity usage. (Volusia Sheriff's Office)

Adams' children, ages 5 and 6, were in the house at the time. 

"You got a 5- and 6-year-old that likely witnessed their father getting murdered," Henderson added. "This was a senseless murder that did not have to occur."

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The exes lived together in the house in Deland, Florida — about 40 miles north of Orlando — after they had divorced. They planned to sell the property and split the proceeds. 

Michael Williams stands on a road with his hands up.

A still from police body camera footage showing the arrest of Michael Williams in Deland, Fla., after he allegedly gunned down his ex-wife and her son. (Volusia Sheriff's Office)

Williams called 911 after the shooting and told investigators that he used the gun to defend himself after his ex-wife and stepson violently attacked him.

"I’ll let the picture speak for itself," said Henderson, holding up a booking photo that showed Williams' unmarred face. "I don’t see anything on this guy."

Michael Williams in a booking photo

A booking photo of Michael Williams after he allegedly murdered his ex-wife and her son in an argument over electricity usage at their home in Deland, Fla. (Volusia Sheriff's Office)

The only weapon found on the property was Williams' gun. Williams and his ex-wife were married for 10 years and had no children together, officials said.

In the last year, police responded to five domestic disputes at their home, but there were no allegations of violence.

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Williams' criminal record includes allegations of child abuse, domestic violence and battery on a law enforcement officer, authorities said.