It happened around 11:30 p.m. Thursday at a home in the 300 block of Norman Drive in Glasgow, Delaware at the Eagle Trace townhomes.
According to investigators, 57-year-old Gregory Thompson broke into the home and began assaulting the 52-year-old woman while she was sleeping in bed.
The victim, who is active with the New Castle County victim advocates, armed herself with a gun and shot her husband, killing him, police said.
Arriving officers say they found Thompson dead in the bedroom and discovered the victim had apparent injuries to her face.
The investigation has revealed the victim had an active protection from abuse order against her ex-husband due to previous violent encounters. At the time of his death, he was wanted by police for violating the order and for causing significant damage to her car.
Police say no charges have been filed.