Steve DelBianco flew out to California two months ago to check on how his son was doing in basic Navy SEAL training. He left a couple of days later, feeling reassured.

Danny DelBianco, who had spent years preparing for this moment, seemed to be acing one of the world’s most grueling mental and physical endurance tests.

He had completed the obstacle course and other physical elements on his first try, “so he was ready to go” for Hell Week, the arduous culmination of the first phase of SEAL training, DelBianco told NBC News. “He was excited and very confident.”

That was the last time he would see his son alive. After 50 hours without sleep and a punishing series of drills, Danny DelBianco, who’d played rugby at the University of Southern California, couldn’t take any more. Like most of the young men who attempt it, he rang a ceremonial bell and dropped out of the punishing SEAL training course. He placed his green helmet in a line next to the ones worn by other drop-outs, and walked toward the barracks.