MANSFIELD, Texas -- Just feet from his driveway, Jeff Wempa points at the spot where his dog was shot and killed.

"All of a sudden I heard a loud crack. I knew it was a gunshot. That's when all the mayhem broke loose," Wempa said.

Caesar, a six-year-old Great Dane, was shot and killed by an off-duty Mansfield police officer Sunday night.

At about 7 p.m., the police officer was walking his own dog and tells investigators that Caesar charged the pair in an aggressive manner.

"The dogs were aggressively barking at each other, but Caesar was not in any attack mode to the police officer -- two dogs doing what they do," said Wempa's wife Carol Evans.

According to Mansfield police, the officer claims to have given a verbal warning before pulling the trigger.

"For him to take out his service weapon and kill my dog in front of children that's playing less than ten feet from him, that's what I want answers to," Wempa said.

Wempa and his wife Carol Evans aren't waiting for answers. On Tuesday morning, they went to police headquarters. Inside they learn internal affairs has launched its own investigation, while the case itself has been turned over to the Tarrant County Sheriff's Office.

The officer involved in the shooting is still working but has been placed on restrictive duty.

"So much devastation. He was our family. He was a part of this family, a family member. He did not have to die this way," Evans said.

The family said they know the officer who pulled the trigger, but they are not naming him. They say they've lived the same neighborhood for nine years.