When he visited his mother in Louisiana in October 2010, he seemed agitated, “not in a good place,” she said. He had begun taking antidepressants and seemed worried that his dream of joining the elite Army Rangers was becoming vanishingly distant. Adding to his stress, he was scheduled to deploy to Afghanistan the next March.

“He didn’t want to go,” Ms. Taylor said. “It didn’t have to do with the war or the Army. He felt like he needed to get his life straight.”

As Christmas approached, Ms. Taylor learned that he had asked his fiancée to enter into a suicide pact. She told his commanders at Fort Bragg, and they promised to put him on suicide watch.

But a mental health professional at the post decided that he was not suicidal and cleared him to go on holiday leave, Ms. Taylor said. Over the next day, he stabbed a drug dealer while trying to reclaim a Rolex watch, a cherished gift that he had traded for drugs, his mother said.

His sergeant, whom he told about the stabbing, took him to turn himself in. But on the way to the police station, Specialist Hook called his fiancée and said, “I’ll see you on the flip side.” Then he stepped from the car and shot himself using a pistol he had taken from a friend. He died on Christmas Day at the age of 20.

Ms. Taylor acknowledged that many of her son’s problems had predated enlistment. But she is haunted by a tape loop of questions about whether she, or her son’s friends, or his commanders, could have done more to help him.

“There is enough blame for everyone to go around,” she said. “The only reason you can blame anyone at all is that he was so young. If he was 40 and pulling these stunts, you’d say he should have learned. But he wasn’t.”