ST. GEORGE — An out-of-control vehicle hit a family of four Sunday afternoon, killing a 9-year-old boy, and struck seven cars and hit the Monhegan Boat Line building on the wharf in the village of Port Clyde.

Emergency crews from several towns and two LifeFlight of Maine helicopters were called around 2:45 p.m. to the scene where a motorist lost control of a vehicle and hit one vehicle before pushing a pedestrian into the building on the wharf, according to a statement from the Knox County Sheriff’s Office. The motorist then continued down the wharf and struck six other vehicles as well as four family members who were walking on the structure. One family member died and two others were airlifted to a Portland hospital, according to the statement.

Chief Deputy Tim Carroll of the Knox County Sheriff’s Office said some of the victims were taken to PenBay Medical Center in Rockport.

John Ferguson, a 17-year-old from Tenant’s Harbor, said that he followed a police car to the wharf just after the accident and found a disaster scene.

“It was definitely chaotic at first,” he said. “No one really knew what happened.

“It was brutal,” Ferguson added.

A longtime volunteer firefighter who was working at the scene but didn’t want to be identified said that he’s seen a lot of bad scenes, but the Port Clyde wharf accident was among the worst of his career.

Both he and Ferguson said that Sunday afternoons in August are generally busy times in Port Clyde, with lots of summer residents and visitors. Ferguson said that the boat for Monhegan was about to leave right about the time of the accident.

“I’m hoping everybody will be OK,” he said. “St. George and all the responding towns did a very good job. They were on the scene within 10 minutes. They were there almost immediately.”

It was unclear what caused the driver to lose control of the vehicle and authorities are withholding the names of those involved pending family notification.

A Knox County emergency dispatcher said that crews from Rockland Ambulance, Knox County Sheriff’s Office, Maine State Police, South Thomaston Fire Department and St. George Fire and Rescue went to the crash scene, in addition to the two emergency medical helicopters.