A dog is now under the watch of animal services and its owner is being question by police after the pet was accused of viciously attacking people in Vaughan.

Police say a 100-pound German shepherd was left untied outside a store at 80 Glen Shields Ave., when it attacked three people Wednesday morning near Dufferin Street and Steeles Avenue.

A 66-year-old man required 20 stitches after he was attacked. The dog also injured a teenage girl.

Helen Zhu, 16, says she was shocked when the dog attacked her as she walked to school through a nearby park.

"People should really look after their dogs, especially if it's a big dog," Zhu says.

The teen suffered only a few puncture marks on her shoulder, she says.

The animal also attacked a 41-year-old woman but she was able to evade the pet.

Det. Const. Alex Samitz says police found the dog and its owner after following up on an anonymous tip.

Samitz says are working with enforcement officials to determine if any charges will be laid.

Anyone with information is asked to call York Regional Police at 1-866-876-5423, ext: 7441.