James Gray, who is dating a DA investigator, was arrested on a charge of aggravated assault with a deadly weapon in the shooting of Derrick Hunt.

DALLAS — Editor's note: This story has been thoroughly updated with additional information and clarification from court records. The video above is from early Friday morning, before many details were known.

A 41-year-old man is accused of using a district attorney investigator's gun to shoot a man he witnessed hitting his girlfriend.

James Gray, who is dating a DA investigator, was arrested on a charge of aggravated assault with a deadly weapon in the shooting of Derrick Hunt.

Hunt, who remains hospitalized, will face a family violence assault charge, arrest records show.

The shooting happened around 10:45 p.m., shortly after Michelle Baptiste, a Dallas County investigator, pulled into the parking lot of the Parkford Oaks apartments in the 3400 block of Mahanna Street near Lemmon Avenue, police said.

Hunt was already at the apartment complex, records show. He knocked on the door of the apartment Gray and Baptiste share, and Gray and Hunt got into an argument, according to an arrest warrant affidavit.

When Hunt saw Baptiste parking, he went to the parking lot, where he attacked her. Gray saw what happened, went to the parking lot and reached into Baptiste's car and grabbed her firearm, the warrant says.

Police said the weapon was in the front seat of the investigator's vehicle.

Gray then shot Hunt in the leg, and Hunt fell to the ground. Baptiste took her gun back from Gray, the warrant says.

Gray then kicked Hunt in the head "rendering him unconscious," the warrant says. Gray then left the scene.

Officers found Hunt bleeding from injuries to his leg, face and arm. Baptiste, who was in uniform, told officers she was calling Gray to tell him to come back to the parking lot, records show.

During an interview with investigators, Gray admitted he shot Hunt, the warrant says.

The DA's office is also investigating, officials said.