The fourth suspect in a violent attack on a woman that left her dog severely injured has turned himself in, say police.

Police say they were called to a reported break-in near 117th Avenue and 80th Street around 6:30 p.m. Tuesday.

When officers arrived, they were told four men tried to push their way into the home of a female acquaintance after a discussion turned violent. One of the men brought out a machete.

As the men tried to enter the home, the woman’s 4-year-old pit bull Mercy lunged in to protect her owner, absorbing the worst of the attack. She received several life-threatening wounds.

After Mercy’s intervention, the men fled.

Mercy was taken to an emergency veterinarian clinic where she required immediate surgery to save her life. She is now recovering, but is on an IV drip and painkillers.

Mercy's owner herself received only minor injuries.

Dr. Brent Jackson, who treated Mercy, said she received two serious gashes from the machete.

“The wounds had gone through the skin and fat and muscle and down to the bone, so they were definitely were intending to do significant harm to her in the attack,” he said.

Police chip in to help cover dog's medical costs

Edmonton Staff Sgt. Randy Wickins is commending Mercy for defending her owner, saying the outcome of the situation could have been very different.

EPS Staff Sgt. Randy Wickins said the attack on the home could have ended very different had Mercy not intervened. (CBC)

“Anything's possible ... I don't know where this assault would have ended – but I think the assault on her was effectively stopped by the dog.”

Police officers later chipped in about $400 to help cover the cost of the expensive procedure.

“It was the downtown division police officers just pulling together knowing they needed to make something happen and they did it,” said Wickins.

“We are relieved the surgery was successful and she is expected to make a full recovery.”

Detectives and officers worked throughout the night to track down the four suspects, arresting two males and one youth by the morning. The fourth suspect, a 19-year-old man, turned himself in around 7 p.m. Wednesday.

Each of the four suspects is charged with break and enter to commit assault with a weapon, possession of a weapon dangerous to the public and cruelty to an animal.