Family members of three people slain by a 14-year-old on newsman Sam Donaldson's New Mexico ranch sued the makers of the video game "Grand Theft Auto: Vice City" on Monday, claiming the crimes would not have occurred had the teenager never played the violent game.

The $600 million lawsuit names several companies and Cody Posey, who it alleges played the game "obsessively" for several months before he shot his father, stepmother and stepsister in July 2004. Posey, now 16, was sentenced earlier this year to state custody until he is 21.

The games and others in the "Grand Theft Auto" series depict police killings and other acts of violence. The lawsuit calls various editions of the game "virtual reality murder simulators."

"But for Posey's use of these products ... he would not have killed," the lawsuit claims.

The game trained him "how to point and shoot a gun in a fashion making him an extraordinarily effective killer without teaching him any of the constraints or responsibilities needed to inhibit such a killing capacity," according to the suit.

According to the suit, plaintiffs' lawyer Jack Thompson was told by a sheriff's deputy that the game and a Sony PlayStation 2 were found at the ranch.

Posey had told police he shot his family after his father, the ranch foreman, slapped him for not cleaning horse stalls fast enough. Prosecutors described Posey as a ruthless killer, but his lawyers claimed his father had abused him for years.

The plaintiffs accuse the corporate defendants — Sony Corporation of America, Take-Two Interactive Software Inc. and its subsidiary, Rockstar Games — of a "civil conspiracy," saying they should have foreseen their entertainment "would spawn such copycat violence."

"We believe the suit is without merit and we will strongly defend the company," Take-Two spokesman Jim Ankner said.

The Associated Press left a message Monday at Sony's New York headquarters seeking comment.

The lawsuit was filed by Verlin Posey of Texline, Texas, representing the estate of the teen's father, Delbert Posey; and Pat and Leona Basham of Elephant Butte, parents of Tryone Posey and grandparents of Marilea Schmid.

Thompson also is the attorney in a $600 million Alabama lawsuit against Rockstar, Take-Two and Sony that blames "Grand Theft Auto" for the 2003 murders of two police officers and a dispatcher at a rural police department. Devin Moore, now 20, was convicted of murder and sentenced to death in that case.