The Maine Warden Service is investigating after a dog was shot and killed in North Yarmouth late Friday morning.

Three people were walking with their dogs on a marked trail in the Knight’s Pond Preserve around 11 a.m. when someone shot one of the dogs, which had wandered a few yards ahead of the group, Maine Department of Inland Fisheries and Wildlife spokesperson Mark Latti said in a statement Friday evening.

It’s not clear who shot the dog, Latti said. He described the shooter as a man in his 30s with dark hair and scruffy facial hair, and added that a man matching that description was seen leaving the area in a dark, full-sized pickup truck.

Inland Fisheries and Wildlife Commissioner Judy Camuso said the shooting was “heinous and inexcusable, and is aggravated by the cowardly act of the shooter fleeing the scene.”

“The incomprehensible and appalling act of one individual tarnishes the reputation of all of Maine’s 230,000 hunters,” Camuso said.”We all are outraged by this atrocity.”

Maine Operation Game Thief is offering a $2,000 reward for information leading to the shooter’s arrest, Latti said. Officials are asking those with security cameras near Henry Road and Edna Lane to check their footage for views of the truck fleeing.

Cumberland police Chief Charles Rumsey, in a statement on social media, said the warden service is leading the ongoing investigation but did not provide specific details  about who was involved or what occurred.

Knight’s Pond Preserve is a 212-acre parcel in North Yarmouth and Cumberland that allows hunting and other recreational uses. The rifle hunting season for deer in Maine ends Saturday.

Anyone with information is urged to call the warden service at 207-624-7076.