HOUSTON -- A father was fatally shot when he stepped outside his northwest Harris County Home to turn his car alarm off, authorities told KPRC Local 2.

A friend told investigators with the Harris County Sheriff's Office that Jesse Tirrell, 21, and a male friend whose name has not been released were inside the Champions Green Apartments complex on Champions Drive when Tirrell's car alarm sounded at about 3 a.m.

Investigators said when Tirrell and his friend walked outside to turn the alarm off, another man waiting in the parking lot opened fire, killing Tirrell.

The witness alerted Tirrell's wife, who called 911 for help. However, by the time emergency crews arrived, Tirrell had died.

Authorities said the gunman might be the ex-boyfriend of Tirrell's wife.

"He was on the only person that fired any shots, but the vehicle was driven by someone else. So, we believe that there was possibly two suspects in the van," Sgt. James Parker said.

The getaway vehicle is being described as a silver minivan or Chrysler PT Cruiser.

Tirrell is survived by his wife and young child.