A San Francisco-bound jet was diverted to Portland after the crew says an off-duty pilot riding in a spare cockpit seat tried to shut down the plane's engines. (AP Digital Embed)

PORTLAND, Ore. (AP) — An off-duty airline pilot riding in an extra cockpit seat on a Horizon Air flight said “I’m not OK” just before trying to cut the engines midflight and later told police he had recently taken psychedelic mushrooms as his mental health worsened, according to charging documents made public Tuesday.

State prosecutors in Oregon filed 83 counts of attempted murder against Alaska Airlines pilot Joseph David Emerson, 44, on Tuesday just before he appeared in court, with his attorney, Noah Horst, entering not guilty pleas on his behalf. Federal prosecutors meanwhile charged Emerson with interfering with a flight crew, which can carry up to 20 years in prison.

According to a probable cause statement filed in Multnomah County Circuit Court, Emerson told Port of Portland police following his arrest that he had been struggling with depression, that a friend had recently died and that he had taken psychedelic mushrooms about 48 hours before he attempted to cut the engines. He also said he had not slept in more than 40 hours, the document said.

Police reported that Emerson did not appear to be intoxicated at the time of the interview, and in a statement Tuesday, Alaska Airlines, which owns Horizon, said neither the gate agents nor flight crew noticed any signs of impairment that might have barred him from the flight. An FBI agent wrote in a probable cause affidavit in support of the federal charge that Emerson “said it was his first-time taking mushrooms.”

While psilocybin is illegal in most of the country — Oregon legalized it for adults this year — the Food and Drug Administration in 2018 designated it a “breakthrough therapy” that might be used for mental health conditions or substance use disorders.

Emerson, an Alaska Airlines pilot from Pleasant Hill, California, was arrested Sunday night after the flight crew reported that he attempted to shut down the engines on a Horizon Air flight from Everett, Washington, to San Francisco while riding in the extra seat in the cockpit. The plane was diverted to Portland, where it landed safely with more than 80 people on board.

The FBI affidavit said Emerson, who as an off-duty pilot was authorized to ride in the cockpit’s jump seat, made casual conversation with the captain and first officer when the plane was between Astoria, Oregon, and Portland, before trying to grab two red handles that would have activated the plane’s fire suppression system and cut off fuel to its engines.

After what the flight crew described as a brief struggle, lasting only about 30 seconds, Emerson left the cockpit, the FBI said.

Flight attendants placed Emerson in wrist restraints and seated him in the rear of the aircraft, but as the plane descended, he tried to grab the handle of an emergency exit, according to the document. A flight attendant stopped him by placing her hands on top of his, it said.

Alaska Airlines said Tuesday that Emerson had been relieved of all duties.

The captain and first officer told police after the plane landed that Emerson said “I'm not OK” just before he reached up to pull the handles. They were able to stop him before he pulled the handles all the way down, the affidavit said.

Emerson walked calmly to the back of the plane after being told to leave the cockpit and told a flight attendant, “You need to cuff me right now or it’s going to be bad,” the affidavit said. Another flight attendant heard him saying, “I messed everything up” and "tried to kill everybody.”

According to the affidavit, he asked police if he could waive his right to an attorney: “I’m admitting to what I did. I’m not fighting any charges you want to bring against me, guys.”

He also told them he thought he was having a nervous breakdown and said: "I pulled both emergency shut off handles because I thought I was dreaming and I just wanna wake up,” according to the affidavit.

Pilots are required to undergo psychological screening as part of their regularly scheduled medical exams. There have been crashes that investigators believe were deliberately caused by pilots. Authorities said the copilot of a Germanwings jet that crashed in the French Alps in 2015 had practiced putting the plane into a dive.

Emerson took his most recent exam in September, Federal Aviation Administration records show — but according to the charging documents, he had long been struggling with depression.

Emerson was to remain in state custody pending an initial appearance in U.S. District Court in Portland, the U.S. attorney's office said in a statement.

Mark Angelos, a senior flight instructor at the NRI Flying Club in Concord, California, has known Emerson for more than 10 years. Emerson used to be president of the club and designed its safety program, meaning he was in charge of making sure instructors followed standard operating procedures, Angelos said.

Angelos said that when he and other club members initially heard the news, they thought Horizon Air must’ve been conducting some sort of emergency drill. They couldn’t believe that a person they saw as a family man who loved his children could be accused of such a thing.

“We thought the airline was conducting a test of its crew, to be honest,” he said. “We know now it was not.”

Lost for words, he expressed his shock. “It just couldn’t have been our Joe.”

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Johnson reported from Seattle.

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