An off-duty police officer and his mother have been charged with murder in connection with a deadly double shooting in the parking lot of a McDonald's in Waldorf, Maryland, that authorities say stemmed from a custody dispute involving the officer's children. The victims were the children's mother and her new husband.

Richard Conway, 26, a Prince George's County police officer, was arrested at his mother's home Monday night. He has been charged with murder of 25-year-old Robert Michael Mange and the shooting of Mange's 24-year-old wife, Prince George's County Police Chief Mark Magaw said in a statement Tuesday.

Conway is the second person charged in the case. Last week, authorities charged his mother, 51-year-old Caroline Conway, with the murder of Mange, and the attempted murder of Mange's wife. The wife had a prior relationship with Richard Conway.

The Charles County Sheriff's Office says that although it was Caroline Conway who fired the weapon, her son participated in the crime before and after the shootings. Investigators say the motive appears to be an ongoing child custody dispute between Richard Conway and the female victim.

On the evening of May 20, the victims drove from Virginia to the McDonald's in the 11000 block of Mall Circle to pick up the wife's two young children. The children had been staying with Caroline Conway, who is the grandmother of one of the children.

Caroline Conway allegedly got into the couple's car and shot Mange, according to the Charles County Sheriff's Office. Her son took her there but stayed in the car with his children, News4's Chris Gordon reported.

"Miss Conway produced a handgun and shot the male victim, Mr. Mange," Charles County Sheriff's Office Capt. Stephen Slavas said. "The female victim tried to flee the vehicle. As a result, Miss Conway, the shooter, shot the female victim in the back."

Both victims were taken to an area hospital, where Mange died. The woman is expected to survive, authorities said.

After the shooting, investigators found ammunition consistent with a .40 caliber handgun, the same weapon issued to Prince George's County Police officers.

The gun used in the shooting has not been recovered. Detectives are looking into the possibility that Conway's service weapon was used in the crime.

The charging document against Officer Conway says his mother told a witness she shot the mother of Conway's children with his service weapon and that he sent text messages to Mange's wife as if nothing had happened though he knew she was shot.

Richard Conway has been with the Prince George's County Police Department for three years. He has been suspended without pay, Magaw said.