CAMBRIDGE, Mass. (AP) _ A jury rejected an insanity defense Tuesday and convicted a man of fatally shooting his girlfriend's three sons in the head.

Vuthy Seng, 34, was found guilty of murder and sentenced to three life terms.

A fourth child, now 16, escaped and recovered from a gunshot wound in the head. She was the prosecution's key witness.

Relatives said Seng was angry after girlfriend Chhong Yim told him to move out of her apartment because her children didn't like him. She left the house after an argument, leaving the children alone with Seng.

He killed the youngsters, ages 9, 12 and 15, in the living room. The oldest was also slashed in the head with a machete.

The defense conceded Seng shot the children but said that he suffered a head injury when a stack of crates fell on him in 1993 at a bottling factory where he worked, and was hearing voices.