New Castle County police officers were called to the Paladin Club Apartments just before 1:30 a.m. Sunday.
Officers found 46-year-old Joseph Connell and his wife, 39-year-old Olga, suffering from gunshot wounds.
Both were pronounced dead a short time later.
Family members believe they were returning home after celebrating the birthday of a friend.
The couple got married last June.
They both worked at C & S Auto Service on Concord Pike.
Olga was the receptionist and Joseph was a mechanic.
Joseph worked alongside his longtime business partner Chris Rivers.
A distraught Rivers told Action News Monday he could think of no one who would want to harm Olga or Joe.
"He was a great guy. He worked hard. He came to work every day," Rivers said.
Anyone with information is asked to contact the New Castle County Police Department at 395-8110 or call Crime Stoppers at (800) TIP-3333.
Tips can be anonymously submitted online by going to www.NCCPD.com and following the link for Tips and Alerts or by texting the key word NCCPD followed by your tip to 847411 (TIP411).
Information from: The News Journal of Wilmington, Del.