A truck driver was involved in a fatal pileup that claimed the lives of four people after swerving on the highway to avoid a herd of deer.

The incident happened on Interstate 81 in Oswego County, New York at approximately 11:30 p.m.

According to Syracuse, 38-year-old Charles Howard III was driving his tanker truck north on I-81 near mile marker 126 when multiple deer entered the highway, causing the driver of the truck to swerve. The sudden move caused the trucker to lose control of the rig and the jackknife across the highway, blocking both northbound lanes.

Two vehicles that were traveling behind the semi truck then crashed into the side of the rig, forcing the vehicles underneath the tanker.

The first vehicle, a 2002 Mercury, went completely underneath the trailer and came out the other side, eventually stopping in a ditch on the side of the road.

The second car, a 2011 Subaru, also passed beneath the trailer, continuing for over 150 feet before stopping in the median.

Three ambulance workers were riding in the Mercury car when it crashed. Corey Moore, 50, Gregg Williams, 58, and Roderick Cota, 63, all worked for R.B. Lawrence Ambulance. All three died in the accident.

Moon John Kim, a radiologist at a local medical center, was driving the Subaru when it passed under the tractor trailer. He was killed in the accident as well.

The truck driver, Charles Howard III, was not injured in the collision.

The exact number of deer that caused the truck driver to swerve is still not known, but police say there were “several.”

“It appears they [the motorists] didn’t see the tractor trailer, the tanker itself, crossing the highway,” said Trooper Jack Keller after the accident.

“It’s pitch black out here in the middle of the night,” he continued. Troopers believe the two cars struck the tractor trailer at speeds of nearly 70 miles per hour.

The north side of I-81 was completely shut down until about 7 a.m. Thursday morning.

An investigation into the details of the accident is still underway.