The Boeing whistleblower found dead in Charleston, South Carolina, in between depositions over the weekend showed no indications he would take his own life and was in good spirits, according to his attorneys.

John Barnett, a 62-year-old longtime Boeing employee who went public with safety concerns he said he uncovered at the North Charleston plant, died Saturday, a day after sitting for a deposition with the company's lawyers. He was supposed to answer more questions but failed to show up. Then police made a grim discovery.

Charleston police said in a statement they responded to the Holiday Inn on Savannah Highway and found Barnett dead in his truck around 10:20 a.m. Saturday. He had a gunshot wound to the head and was pronounced dead at the scene.

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The coroner's office told Fox News Digital that he died from what appeared to be a self-inflicted gunshot wound. The official coroner's report was not yet available. City police said they were investigating the circumstances of his death.

"We are all devastated," his attorneys, Robert Turkewitz and Brian Knowles, told Fox News Digital.

WATCH: John Barnett raises safety concerns in January interview with TMZ

"We need more information about what happened to John. The Charleston police need to investigate this fully and accurately and tell the public what they find out. No detail can be left unturned."

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They said Barnett was planning to complete his deposition and move on with his life after his decades-long Boeing career ended in a retaliation lawsuit after he uncovered and went public with safety problems in the 787 Dreamliner, they said.

"He was in very good spirits and really looking forward to putting this phase of his life behind him and moving on," they said. "We didn't see any indication he would take his own life. No one can believe it."

Barnett worked for Boeing for over three decades before retiring in 2017 as a quality control engineer. In 2019, Barnett told the BBC that Boeing would rush to get its 787 Dreamliner jets off the production line, compromising safety.  

He alleged the emergency oxygen systems on the jets had a failure rate of 25%. This meant that a quarter of 787 Dreamliners had the potential to rapidly lose oxygen if the cabins were suddenly decompressed, suffocating passengers.

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He said he learned of the issue while working at Boeing's North Charleston plant in 2010 and claimed to have raised the issue with management to no avail. Instead of tackling the issue, his lawyers allege, the company retaliated against him and subjected him to a hostile work environment, leading to the lawsuit for which he was being deposed.

The Federal Aviation Administration reviewed Boeing in 2017, corroborated some of Barnett's allegations and ordered the company to take action.

In a statement, Boeing told FOX Business, "We are saddened by Mr. Barnett’s passing, and our thoughts are with his family and friends." 

This past January, Barnett told TMZ he was concerned that Boeing was returning its 737 Max 9 jets to the sky too quickly, after the incident in which an Alaska Airlines jet's door panel blew off midflight.

"John was a brave, honest man of the highest integrity," the lawyers said. "He cared dearly about his family, his friends, the Boeing company, his Boeing co-workers, and the pilots and people who flew on Boeing aircraft. We have rarely met someone with a more sincere and forthright character."

The investigation remains ongoing.

"Detectives are actively investigating this case and are awaiting the formal cause of death, along with any additional findings that might shed further light on the circumstances surrounding the death of Mr. Barnett," Charleston police said in a statement.

If you or someone you know is having thoughts of suicide, please contact the National Suicide Prevention Lifeline at 1-800-273-TALK (8255)

Fox News' Andrea Vacchiano contributed to this report.