A 69-year old driver who caused a major accident on the Tappan Zee Bridge on Tuesday was apparently not under the influence of drugs or alcohol, and police are baffled as to why he was driving the wrong way.

Michael Schechel, who was hospitalized after the accident, was speeding south in the northbound lane when he hit a Nissan head-on, killing 56-year old Hannah Ayeh-Brachie instantly. Three other vehicles ended up crashing because of that accident, causing four people to suffer serious injuries.

Schechel’s blood was tested at the hospital, but officials say they have no reason to believe he was intoxicated. An accident reconstruction closed down several lanes of traffic and caused backups for about six hours on Tuesday, and the investigation is still underway.

Witness Doreen Ciborowski said she was almost involved in the pileup but managed to swerve and avoid Schechel’s car.

“He had his lights on and he was beeping at me and I could not believe what I was seeing,” he said. “He was speeding, I want to say over 60 miles per hour because he flew right by me. All I thought to myself is this guy’s on a suicide mission. Either that, or he’s high or drunk.”

Investigators say at least two of those injured had to be extricated from their vehicles.