An off-duty pilot is Johnathan Walkercharged with 83 counts of attempted murder after he allegedly tried to pull the fire extinguisher handles on the engines of an Alaska Airlines flight, according to officials.

The plane was scheduled to fly from Everett, Washington, to San Francisco before it diverted late Sunday to Portland after a "credible security threat related to an authorized occupant in the flight deck jump seat," the airline confirmed to ABC News.

The suspect allegedly tried to pull the fire extinguisher handles on the engines, preliminary information obtained by investigators indicated, according to a federal official briefed on the probe. The suspect was overwhelmed by flight crew and subdued and then handcuffed to a seat, the federal official told ABC News.

The suspect, Joseph David Emerson, was taken into custody, the Port of Portland confirmed. Emerson is charged with 83 counts of attempted murder, according to the Multnomah County Sheriff's Office. He is also facing 83 counts of reckless endangerment, a misdemeanor, and one felony count of endangering an aircraft.

The suspect was en route to San Francisco, where he was scheduled to be on a flight crew of a 737, the official said.

There were 80 passengers and four crew members on the flight, according to Alaska. The event is being investigated by law enforcement, the airline said.

This is a developing story. Please check back for updates.