A photo of Michael Diamond at age 4

San Francisco Bay area -- It was, at the time she says, the very worst day of Patricia Perillo's life. Her son Michael Scott Diamond, then 15, had just been diagnosed with bipolar disorder and schizophrenia.

She could not have realized it at the time, she remembers, but there were to be many more worse days to come. The worst came last week when she learned that her son, now 35, had been arrested on suspicion of killing a roommate at a Cherryland independent living facility for people with psychiatric disabilities.

According to court records, Diamond allegedly strangled 50-year-old Dong Tran on Oct. 7 with two rubber bicycle tire inner tubes that he had tied together. Diamond, who is charged with murder, is being held without bail at Santa Rita county jail in Dublin.

"My son Michael would not do this and I'm being straight with you,'' Patricia Perillo, 56, said in a recent telephone interview from her home in Plymouth, Mich. "He did not commit this crime. His illness did." She and other family members said they wanted to express their condolences to Tran's relatives.

While Tran's death is a tragedy, Diamond's struggle over the past 20 years with debilitating mental illness itself tells the story of a man just seeking to be normal, of a mother wanting her son to be safe and of a family feeling powerless in their desire to help their loved one.

Perillo likes to remember those days before the illness took hold and transformed her son.

"Mike was a normal, happy little boy and teenager until this happened,'' she said. "You'd have to have seen him. He was a joy, he was loved by so many people, loved to save money, was a hard worker, good in school, great in sports."

Perillo, who split with Diamond's father, Dan, when the boy was 3, moved with her family to Arizona when Diamond was about 9 or 10.

Michael Diamond as a Little Leaguer in Utica, Mich., in 1977

Richard LeClair, 38, Diamond's older half-brother, who enlisted in the U.S. Navy as a teenager, remembers coming home on leave at about that time and being overcome with emotion at the sight of his brother.

"To be honest with you, when I saw him I cried," LeClair said. "The Mike I knew was gone."

Perillo initially thought her son was using drugs, and she brought him to see doctors, neurologists and psychologists. His weight began to drop, from about 130 pounds to 93. Finally, after about six months of searching for answers, a psychiatrist gave Perillo her son's diagnosis: bipolar disorder and schizophrenia.

The psychiatrist told Perillo that her son would never be "normal" again.

As devastating as the news was, Perillo said she was determined that she could somehow solve the problem.

"I said, 'I'm going to fix it - find Mike a job, we're going to make it better,'" she said. ``It just didn't work that way."

She was then only taking the first steps in a long, frustrating and heartbreaking journey that continues to this day.

One major frustration, Perillo said, is that she largely lost her ability to be involved in her son's medical care decisions once he turned 18.

Despite some "great years" for Diamond - whose illness includes hearing and seeing things that do not exist - there have been numerous hospitalizations over the last two decades, some scrapes with the law and drug use, family members said. Perillo keeps his voluminous medical records in a massive box.

All that time, Perillo said she dedicated herself to doing her best to make sure her son was safe.