State police are investigating the weekend crash between an Amish horse-drawn buggy and a logging truck that killed a young boy and his mother and injured his father and two siblings in southern Venango County.

The accident happened abut 3:05 p.m. Sunday on Route 208 in Irwin Township, authorities said, about two miles north of the Butler County line.

The buggy was carrying a family of five and was traveling east on the 2400 block of Route 208, also known as Clintonville Road, police said, when it was struck from behind by the log truck. The tri-axle Peterbilt truck was empty.

Authorities have not released the names of the Amish family or the truck driver.

Venango County Coroner Christine Rugh pronounced the boy, believed to be in the second grade, and his mother, believed to be in her early 30s, dead at the scene. Autopsies were to be performed Monday, Rugh said.

The boy's father, who was driving the buggy, and one of his sisters were flown by medical helicopter to St. Elizabeth Boardman Hospital in Youngstown, Ohio, and Children's Hospital in Pittsburgh, respectively. Their conditions were not available.

The boy's brother was taken by ambulance to Grove City Medical Center, where he was treated and released.

The driver of the truck apparently was not injured. Police said he is “cooperating” with investigators. Venango County District Attorney Shawn White also assisted at the scene.

White declined to discuss the investigation or if charges would be filed.

“The investigation is way too premature,” he said early Monday afternoon.

The crash closed a portion of Route 208 for several hours. Authorities said the horse also was killed.

The Clintonville and Emlenton volunteer fire departments, both in Venango County, and the Harrisville and Marion Township volunteer fire departments in Butler County assisted at the scene.