BOSTON -- An Ashland police officer is grateful for man's best friend.

Officer Chris Alberini and his K-9 partner, Dax, were on patrol Wednesday night when they pulled a car over for swerving.

Police said the driver, Timothy Sullivan, started yelling at the officer and took off when the officer got out of the car.

After issuing a warning that he would release Dax, Sullivan allegedly came out of the woods and physically attacked the officer, police said.

Dax was still in the cruiser, but the front window had been left down as a precaution. Alberini gave the command, and Dax made his move.

"(Sullivan) was reaching up and grabbing the dog's face," Alberini said. "As soon as the handcuffs were on, he was given the command to release."

Dax bit down on Sullivan's neck and got him to surrender. Sullivan now faces several charges, including interfering with a police dog, and is being held without bail.