sandra mathis , 52 , surrendered to police just after 4.45 pm in the 1800 block of commercial street after police say she repeatedly plunged a knife into her husband 's upper torso .
the 48-year-old victim was discovered lying on the ground unresponsive with blood gushing from a wound in his neck .
he was taken to ucsd medical center , where he was pronounced dead from his injuries two hours later .