By Anna Giles

STOCKTON (CBS13) — Investigators with the U.S. Marine Corps said a deadly military training exercise that took the lives of seven marines and a sailor from Stockton off the Southern California coast last summer was preventable.

Now, the Marine Corps is launching a second, much broader investigation, after the initial report was released just weeks ago.

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The sailor from Stockton was Chris Gnem, known as “Bobby.” He was a graduate of Lincoln High School, and at the time of this deadly exercise, he was engaged to be married.

Bobby’s mom said he spoke of grandkids he would never get the chance to have.

Last summer, Bobby and eight others were training in an amphibious military vehicle near San Clemente Island when the vehicle took on water and sunk.

Bobby’s mom said he went down with the engagement rings he had just purchased for himself and his new fiancé.

“To hear that things happened that could have been prevented, it just makes it that much harder to take,” said Gary Greeno, Bobby’s former basketball coach.

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Experts said the amphibious vehicle should have never been in use.

Marine Corps officials point to a mix of mechanical issues and a failure to properly train those on board. They said in the report that “water entered the amphibious vehicle through multiple points of leakage and bilge pumps were unable to expel water rapidly enough due to transmission failure.”

According to details obtained by the Marine Corps times, those on board “were provided with practically no training on what to do when an emergency happens inside an amphibious vehicle.” They were fighting for their lives with no way to radio for help, again due to equipment failure. They used flags to signal they were sinking.

“It’s just sad, the whole story is sad and knowing Bobby and the kind of kid he was. This just breaks your heart,” Greeno said.

His mother was told his death was completely preventable. A painful revelation, about a man remembered for how he treated others

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“There were multiple times when somebody might be down, somebody’s having a bad game and who was there picking him up and talking to him in his ear, it was Bobby,” Greeno said.