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This story was prepared in partnership with The Virginian-Pilot.

A Navy SEAL trainee drowned after being repeatedly “dunked” underwater by an instructor, according to a San Diego medical examiner's report released Wednesday that labels the death a homicide.

"Although the manner of death could be considered by some as an accident, especially given that the decedent was in a rigorous training program that was meant to simulate an 'adverse' environment, it is our opinion that the actions, and inactions, of the instructors and other individuals involved were excessive and directly contributed to the death, and the manner of death is best classified as homicide," the pathologist wrote.

The May 6 death of Seaman James Derek Lovelace, 21, had not been announced by the Navy until after officials were questioned about it days later by NBC News and The Virginian-Pilot newspaper. Navy officials portrayed it as a training mishap. But sources told NBC News and The Pilot the death was caused by an instructor going too far.

READ: Surge in Reported Near Drownings During SEAL Training

Lovelace was struggling during an exercise in which trainees tread water in the pool wearing combat fatigues and boots, according to the medical examiner’s report. Multiple witnesses told investigators that prior to the instructor laying his hands on Lovelace, the sailor's "face was purple and his lips were blue."

During the exercise, “instructors are reportedly advised to not dunk or pull students underwater,” the report says.

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But in a video of the incident, the report says, “an instructor in the water approaches the decedent and apparently dunks the decedent underwater. Over the course of the next approximately five minutes, the instructor follows the decedent around the pool, continually splashing him with water. The decedent is also splashed by other instructors in the water. Throughout the time period, the decedent is observed to go under the water multiple times.”

Seaman James Derek Lovelace, 21, died during basic underwater demolition/SEAL training, better known as BUD/S. U.S. Navy

At one point, the report says, another student approached Lovelace and tried to help him keep his head above the surface. One individual considered calling a “time-out” to stop the exercise, the report says, but failed to do so.

READ: Navy SEAL instructor Removed From Training After Sailor's Death

"The instructor appears to again dunk the decedent and continues to follow him around the water," the report says. "The instructor also appears to pull the decedent partially up and out of the water and then push him back. Eventually, the decedent is assisted to the side of the pool where he is pulled from the water.”

Lovelace was initially responsive but later died, the medical examiner's report says.

He was in the first week of Basic Underwater Demolition/SEALs training, or BUD/S. The six-month course is considered among the most punishing military training programs in the world, with four out of five trainees failing to complete the program and become SEALs.

Lovelace had joined the Navy six months earlier, walking away from a college baseball scholarship to pursue his dream of becoming a SEAL, family members said.

The coroner’s report lists his death as a drowning, with cardiomegaly as a possible contributing factor. Cardiomegaly, better known as having an enlarged heart, can cause heart failure.

You can reach Ken Dilanian at ken.dilanian@nbcuni.com

The instructor involved, a petty officer first class who joined the Navy in 2008, had continued in his job immediately following the incident. He was removed from duty only after a story by NBC News and The Pilot challenged the narrative initially released by the Navy.

The instructor remains on administrative duty, Navy officials said, and no charges have been filed.

READ: Three Deaths Raise Questions About Navy SEAL Training

Naval Criminal Investigative Service Ed Buice said his agency's investigation into the death is ongoing, and no “conclusions have been reached regarding criminal culpability."

"It is important to understand that 'homicide' refers to 'death at the hands of another' and a homicide is not inherently a crime," Buice wrote in a statement.

A Navy SEAL spokesman declined to comment on the report, citing the NCIS probe and a separate ongoing investigation by Naval Special Warfare Center, which oversees BUD/S and other SEAL training programs.

"Out of respect for the integrity of the investigative process, we can't discuss the ongoing investigations or any of their individual elements," said Navy spokesman Lt. Trevor Davids.

Lovelace was the fifth SEAL in four months to lose consciousness in a BUD/S pool exercise, according to Navy safety data, a significant increase in reported blackouts compared to previous years.

Following the death, Davids said, the command paused training and retrained instructors on safety protocols.