FORT COLLINS, Colo. -- A Fort Collins woman said she rigged up a hidden video camera to catch her daughter's boyfriend trying to suffocate her dog and he pleaded guilty to killing her other dog.

Mark Brien, 19, faces up to 18 months in jail when he is sentenced later this month on charges of cruelty to animals, a felony.

Video

Hidden Camera Catches Suspect

Alicia Larson owned two shih tzus and said that they suffered a series of debilitating injuries that ultimately lead to the death of one of them last summer.

According to an affidavit from the Larimer County Sheriff's Office, in 2004, Larson discovered that one of her her dog's front right paws was dislocated and then later learned the other front paw was dislocated, as well.

A few months later, she found one of her dogs dead in a closet. A necropsy showed the animal died from acute blunt trauma that fractured her ribs and punctured her liver, according to the affidavit.

Larson told investigators she suspected Brien because her dogs appeared afraid of him and their injuries always seemed to occur when he was around.

After her second dog was found wandering around the house last August, foaming at the mouth, she took him to a veterinarian who told her the animal had ingested a caustic substance.

After coming home from the vet's office, Larson put a hidden video camera in her bedroom and focused the camera on the bed, where she placed her dog. She then told Brien she was going out.

She said she went downstairs to the basement to watch the video feed and saw Brien strike her dog on the head with a stone coaster and then try to suffocate it by placing his hand over the dog's nose and mouth.

After running upstairs to confront Brien, she said he admitted killing her first dog and then making her second dog swallow bleach. The second dog is partially blind in one eye and can't eat solid food because of damage to her throat from the bleach.

Brien is free on bond until his sentencing on May 31.