Navy SEAL Trainee’s Sister Vows to ‘Seek Justice for My Brother’ After His Training Death

“I will not stop until that is done,” Price said.

In an exclusive interview with ABC News’ Amy Robach, Lynsi Price alleged that the Navy misled her family about what led to her brother’s death by telling them it had resulted from an accident. She says she felt stunned and “betrayed” to read on Facebook that the medical examiner had ruled the death a homicide.

“I think that my mission in life now is to seek justice for my brother. And I will not stop until that is done,” Price said.

Describing herself as an “Air Force brat,” she stressed that she was a staunch supporter of the military and the Navy, but Price said she wanted to see concrete changes to the SEAL training program so no other family would have to lose a loved one to a training death.

Her 21-year-old brother, James Derek Lovelace, drowned on May 6 after appearing to struggle during a pool exercise at the Naval Special Warfare Center, according to the medical examiner’s report. The medical examiner noted the role that the stressful exercise and aggressive instructors may have played in Lovelace’s death. Video footage of the exercise reviewed by investigators shows an instructor "dunking the decent under water," then following him around the pool to again dunk him and yell at him, the report also read.

As part of the exercise instructors were expected to splash, make waves and yell at the student to create an "adverse" environment. Instructors reportedly were “not to dunk or pull the students under the water,” according to the medical examiner's investigation and report.

Defense officials responded saying that the medical examiner's homicide ruling does not mean a crime had been committed.

A Navy official familiar with the case told ABC News today that determining whether or not instructors were allowed to dunk trainees at such an early stage of SEAL course will be a “critical consideration” in the Navy’s internal investigation.

That investigation is not expected to conclude for at least three months, according to the Navy official.

Price said her brother wrote letters to her detailing his progress. She said he called the training -- which is the military's most rigorous -- “so easy” and was upbeat about his chances of becoming a member of the elite unit. She also said he was in peak physical condition.

His daily pre-Basic Training regimen included a CrossFit workout followed by a 10-mile run before he went to work. He would continue rigorous workouts after work, including swimming with 70-pound weight belts, she said.

“There was no doubt in our mind that he wouldn't go all the way and that he would complete the whole program,” she said.

Suggestions after his death that her brother wasn’t a strong swimmer were “absolutely false,” she said.

“Derek was the best swimmer I've ever known,” she said, adding that anyone who knew her brother would know he “would never drown.”

In one of his letters, she said her brother wrote that he would rather die than quit the rigorous program.

Price and Lovelace’s girlfriend have started the campaign named “Justice for Derek” in his honor. At first, they were soliciting donations so they could travel to tell Lovelace's story but the mission is now to raise money to help boys who want to become SEALs, Price said.

“It was Derek's dream. And I want other people to have that dream,” she said.

In fact, her family had asked Lovelace whether he would be interested in joining another branch of the armed forces. He wasn’t.

“But that was Derek. And that was the type of person he was. He did everything to the extreme...And he wanted to fight for our freedom,” she said.

U.S. Navy officials declined to comment on the family's statements.

ABC News' Luis Martinez contributed to this report.