His problems have been a long time in the making. Psychiatrists can’t even agree on what’s wrong with him. He has been confined in psychiatric hospitals at least 20 times and labeled with almost every diagnosis that could be applied to a person with a history of aggressive behavior: schizophrenia, bipolar disorder, polysubstance dependence, attention deficit disorder, impulse control disorder, antisocial personality disorder and intermittent explosive disorder.

From the time he was a little boy, growing up in the Kingsbridge section of the Bronx, he had uncontrollable rages. He bit teachers, fought with classmates, urinated on hospital staff and refused to go to school for weeks at a time. At age 6, he spent nearly a month at Bronx Children’s Psychiatric Center, a state hospital.

His home life was often unstable. His father, who is also mentally ill, was in and out of prison. In 1990, shortly after his mother gave birth to him at age 16, she moved to Florida, leaving him with his great-grandmother for several years.

Many members of his extended family had mental illness and substance abuse problems. His paternal grandparents were both alcoholics, and his maternal grandfather died after falling out a window — or possibly jumping.

His mother, Shakima Smith-White, acknowledged that she was not always there for her son initially. But she said she re-entered his life full-time when he started school. She has been married now for 20 years, works two jobs and is studying to be a nurse practitioner.

“We weren’t perfect, but we tried with Michael,” she said.

When he was 5, she said, she took him to Miami on her honeymoon, to her husband’s dismay. And when Michael was going through a bad stretch in his late teens, she said, her husband took their two daughters and moved out, worried it was too dangerous to stay. “He pretty much gave me an ultimatum, that it was him or Michael,” she said. “And I chose my son.”

“At the time he needed me more than the girls or my husband,” she said.

When Mr. Megginson was doing well, she said, he was wonderful to be around — calm, affectionate, funny.