The 10-year-old son of a divorced American couple shot his father dead as he was being picked up from his mother's home in Texas, police say.
Personal firearms are widely available in the US
Rick James Lohstroh, 41, died on his way to hospital after being shot several times as he sat in the driver's seat of his car outside the house.
The boy reportedly fired from the back seat and then from outside the car, using his mother's gun.
Friends of Mr Lohstroh, a doctor, said his divorce had been "bitter and ugly".
His former wife was inside the house with another son, aged seven, at the time of the shooting, said Sgt BE Williams of the Harris County Sheriff's Department.
She reportedly took the gun away from her 10-year-old when he came inside afterwards.
The boy, who cannot be identified because he is a minor, has been placed in the county's custody pending a hearing on Monday, the Houston Chronicle reports.
Law officials quoted by the Associated Press news agency said they had been called to the house before in a family dispute.
Mr Lohstroh had arrived at his wife's house on Friday in his sports utility vehicle to pick up his two sons, having joint custody of the boys.
His former wife said later that she did not know how her son had obtained her gun which, she said, was kept locked and unloaded inside the house.
The couple divorced in May 2003 after long legal wrangling and both ex-spouses had since found new partners, the Houston Chronicle reports.
Mr Lohstroh continued to pick up his sons for weekend visits, coming over from his own house about 64km (40 miles) away.
His lawyer, Kathleen Collins, said the divorce case had been one of the worst she had witnessed "in terms of false allegations" and neighbours of the mother spoke of continuing "explosive arguments" outside the home.
Friends and colleagues of the late doctor described him as "much loved and respected".