KINGWOOD, W.Va. (AP) _ A former teacher on trial for three counts of murder says he killed his pregnant girlfriend in self-defense after her son was accidentally shot.

Thirty-six-year-old James DeGasperin took the stand in his own defense Thursday in Preston County.

DeGasperin is accused not only of killing Lori Casteel and her 13-week-old fetus on April 15, 2007, but also Casteel's 4-year-old son Collin.

DeGasperin said during an argument over her drug use, Casteel pointed a shotgun at him and threatened him. He said as he grabbed the gun, it went off and Collin was shot.

Casteel later came after him with the gun, he said, so he grabbed a baseball bat and hit her.

He also said he has no idea what he was thinking when he went back to Collin, and after finding no pulse, hit the child's head with a rock.

The trial resumes Monday.