Police were called at 12:48 a.m. Wednesday to the 100 block of Benham Court, near the Clearview Ridge Townhouses community.
Newark, Delaware resident Steve Bitanga believes he saw a cougar or mountain lion just after letting his boxer named Jake out for a walk. He says he heard a screech and saw a large animal about 30 yards away.
"I can hear the growling and it was definitely a mountain lion, maybe a cougar, but it was pretty big," Bitanga said.
Bitanga says he watched for about 8 minutes and called 911, but didn't snap a photo.
The cougar is one of North America's biggest cats, also called a puma or mountain lion.
"The caller's indicating it's twice the size of a full grown boxers, so it's our obligation to make the public aware," New Castle County Police Officer John Weglarz said.
Neighbors were surprised at the news and said they'd be extra vigilant.
"We've seen deer, we've seen foxes, but never anything like a cougar," resident Casey Graney said.
Police say there have been reports of cougar sightings in the area in the past.