Most recently, the animal attacked 80-year-old Edward Yeninas and his miniature poodle during a morning walk on Patricia Road in Newark.
Yeninas says the dog dragged him down from behind, latched onto his arm, then lunged for the poodle.
Yeninas suffered minor injuries. His poodle, named Yianni, was killed.
A neighbor who stopped to help says if he hadn't interceded, it could have been even worse.
"He's an 80-year-old man. What can he do to a dog like that? He can't defend himself," said William Banks.
"What I don't understand is that if my dog doesn't have a license , they take it to the SPCA. This dog killed my dog and did this to me, and it's in the house," said Yeninas victim.
The Delaware SPCA has not issued a statement on the incident.
Neighbors say this is the second time in a year that the same dog attacked a pet owner and that owner's pet.