In a rather bizarre development, an off-duty pilot is facing several charges related to an incident in which he allegedly tampered with jet engines during an Alaska Airlines flight. The incident occurred on Sunday as the flight went from Everett, Washington, to San Francisco, California.

During the flight, the airline reported a “credible security threat” related to an authorized occupant in the cockpit, which resulted in the flight being diverted to Portland International Airport.

An off-duty pilot riding as a passenger in the cockpit of an Alaska Airlines flight tried to seize control of a plane headed from Seattle to San Francisco on Sunday, the airline and a source familiar with the matter said.

A pilot assigned to the flight told air traffic controllers a person riding in the cockpit of flight 2059 attempted to turn off the aircraft’s engines in flight. Pilots will occasionally ride a cockpit “jump seat” when traveling in an official capacity or commuting to another airport.

Joseph Emerson, 44, has been arrested by the Port of Portland Police Department and charged with 83 felony counts of attempted murder, 83 counts of reckless endangerment and one count of endangering an aircraft, online booking records show.

Emerson is an off-duty pilot who is accused of trying to seize control of the Alaska Airlines flight, a source familiar with the matter told CNN. The airline he works for wasn’t immediately known.

One of the other pilots told air traffic controllers after removing Emerson from the cockpit: “We’ve got the guy that tried to shut the engines down out of the cockpit, and he doesn’t sound like he’s causing any issues in the back right now.”

Following the incident, Alaska Airlines said it is “grateful for the professional handling of the situation by the Horizon flight crew and appreciate our guests’ calm and patience throughout this event.” The airline is cooperating with law enforcement in the ongoing investigation.

Emerson is accused of trying to deploy the fire suppression system before being subdued by crew members.

The most puzzling aspect of this story is Emerson’s motive, which has not yet been determined. What would drive an off-duty pilot, authorized to be in the cockpit, to allegedly try to shut down the engines of a plane full of passengers? Until the investigation is complete, the “why” behind Emerson’s odd and dangerous actions remains a burning question.

Another issue that arises from this story is airline security measures. Should the background checks for authorized cockpit personnel be more stringent and comprehensive? Is it possible that this could lead to changes in federal aviation regulations?

It’s possible. But at the same time, this incident could be considered an outlier, not a reflection of the efficacy of the security system used to determine who should be in the cockpit.

While the passengers aboard the flight experienced a harrowing and terrifying journey, a catastrophic situation was narrowly averted thanks to the crew members and their quick response. With the investigation underway, it is possible we will learn more about what led to this incident.