Members of a U.S. Marine Corps unit involved in a deadly air crash off Shikoku last December frequently engaged in inappropriate activities during flights, such as reading books and taking selfies, a U.S. military report revealed Tuesday.

The report follows the midair collision of a Marine Corps F/A-18 fighter jet and a KC-130 aerial tanker off the coast of Kochi Prefecture on Dec. 6, 2018. The aircraft, which were conducting a nighttime aerial refueling mission, crashed into the Pacific Ocean, killing six onboard.

According to the report, several members based at U.S. Marine Corps Air Station Iwakuni in western Japan were found to have removed their oxygen masks and taken both hands off of the aircraft controls to read books or to groom their beards during flights. In one instance, a pilot was found to have shared a selfie taken during a flight on social media.

In addition, urine samples from members, including one from a pilot involved in the 2018 accident, had tested positive for traces of a hypnotic sedative that made them unfit to fly.

The same unit was also involved in a midair crash off Kadena Air Base in Okinawa Prefecture on April 28, 2016, in which an F/A-18 fighter jet hit an air tanker and made contact with the fueling hose.

The Marine Corps categorized the accident at the time as Class C, the second-least serious in its four-level flight accident assessment system, meaning it was determined that it did not warrant an investigation and that publication regarding the accident was deemed unnecessary. It was not reported to the Japanese Defense Ministry.

The report said that a climate of unprofessionalism in the unit was a factor in the 2018 crash, adding that it could have been prevented by an investigation into the accident in 2016.

Following the investigation, four officers were dismissed including the commanding officer, who was found to have posted a selfie on his WhatsApp profile showing him in flight with his oxygen mask off and his visor up.

Another officer shared a selfie showing him reading a book with both hands off the controls and his mask off, while a third shared a selfie where he was pictured with his mask off and grooming his mustache with a comb. Both images had been taken in-flight, the report said.

The Defense Ministry is calling on the U.S. forces to hand over information regarding the 2016 accident and to ensure safety in future operations. Residents of Iwakuni in Yamaguchi Prefecture expressed anger at the findings of misconduct, with some calling for the suspension of U.S. military flights.

“They’re extremely dangerous behaviors,” said 74-year-old Jungen Tamura, a former member of the Iwakuni Municipal Assembly who monitors activities at the Iwakuni base. “They could cause an accident and (they) need to suspend flights immediately.”

Makoto Ebuchi, a 62-year-old adviser to a citizens group opposed to expanding the scope of functions performed at the Iwakuni base, said, “It’s shocking … I’m horrified. The state and the city need to thoroughly study how to re-educate them.”