WASHINGTON, Dec. 26 (Xinhuanet) -- U.S. police is investigating the motive of a man who killed four people and himself on the Christmas Day near Washington DC.

    Police in the Fairfax County, Virginia, said Monday that the shooter had a history of mental problems, but they are still trying to determine his motive for the rampage, according to reports of CNN.

    On the Christmas Day, Nathan W. Cheatham, a Fairfax resident, shot his mother to death in the driveway of her home.

    He then drove to the home of an acquaintance and killed three people there before turning the gun on himself.

    Cheatham, 27, had been arrested on several occasions by FairfaxCounty police for what they described as "minor infractions."

    Before the shooting, he had been living with his mother for at least two weeks.

    Police believe Cheatham broke into the second home and systematically went from room to room, fatally shooting Janina C. Price, 50, and her son Adam S. Price, 19, and Christopher J. Buro,20, who was visiting.

    Another member of the Price family hid in the basement and escaped the disaster.

    Police said Cheatham had called the Price family earlier in theday for a visit and was refused. Enditem