FAIRFAX, Va. (AP) — A teenager who shot his parents to death as his sister listened helplessly on the phone has pleaded guilty to murder and weapons charges.

Attorneys for Joshua P. Cooke, 19, had planned to argue that their client confused right and wrong because he thought he was living in the virtual reality of the 1999 movie "The Matrix."

On Tuesday, Cooke admitted gunning down his parents inside their Fairfax County home on Feb 17. His sister, Tiffany Cooke, 19, was speaking to her father from Pennsylvania when she heard the shots.

After the shootings, Joshua Cooke hung up the phone and called 911, telling the operator, "I just shot my parents. I just blew them away with a shotgun."

The bodies of Paul Cooke, 51, and his wife, Margaret Ruffin Cooke, 56, were found inside the home. Paul Cooke was the son of Paul P. Cooke, former president of D.C. Teachers College, now the University of the District of Columbia.

Joshua Cooke faces a maximum 20 years to life on the two murder counts. He is due to be sentenced on Aug. 7.