Brutus, an American pit bull terrier, was removed from its owner earlier this month, after it attacked a dog.
While at the animal control centre, Brutus attacked and killed another medium-sized dog, said officials from the District of Okanagan Similkameen.
On Thursday afternoon, he escaped, and officials say there are signs someone broke him out before he was due to be destroyed.
"We believe he was taken. There are signs of a forced entry," said district spokesman Andrew Stuckey.
Although the animal is likely in someone's custody, Stuckey warned he may get loose again.
"He has been released once already, and was running at large when the first attack occurred, so we are concerned, and we are advising people to take extra care with their pets and their small children to make sure they are kept safe," Stuckey said.
Stuckey says anyone who sees Brutus should stay away. Brutus is brown with black stripes, and has a white diamond on his chest.
The warning has alarmed some area residents.
"I'll never understand why people continue to choose to own these dogs," said Tamie Williams, a Kelowna resident whose son was attacked by a pit bull in 2011, leaving him with close to 60 stitches on his face.
"A ban hurts no one. It keeps the public safe," she said.
Animal rights activists say the problem is not the breed itself, but irresponsible owners.
They are calling for legislation that targets all dangerous dogs, regardless of breed.