From the time Ned was born in northeast Nebraska, his family said, they knew he was not like other babies.
"He was more than happy to be just left lying there and didn't like to cuddle," said his grandmother, Mary Thunker, who helps to raise her daughter's five children. "He was never one to be rocked and had little interaction with other kids."
By the time Ned, not his real name, was a toddler he was having full-blown temper tantrums, kicking and screaming in public. As he got older, he attacked his mother with a baseball bat and went after his brother with a golf club.
"We always lived in fear that in the right circumstances he would get aggravated and lose control, and we never knew what he was capable of doing," said Thunker, 59. "We had a safety plan to get the other children out of the house."
After the news last week that 20-year-old Adam Lanza had killed his mother and 26 victims at Sandy Hook Elementary School in Newtown, Conn., Thunker said she thought, "Oh my god -- that could be our family."
Lanza has been described by those who knew him as socially awkward and lacking empathy -- bright, but troubled. A former high school teacher said he suffered from a condition where he felt no pain.
Mark Tambascio, a family friend, told ABC he believed Lanza's mother, Nancy, had become increasingly concerned in the last few months about her son's emotional and behavioral issues.
Thunker said she understands how difficult it is to deal with a troubled child and to get proper treatment in a mental health care system that is fragmented and not well funded.
Today, Ned is 15 and is stable and living at home after two hospitalizations -- one at only age 7 -- and more than a year of residential treatment at Boys Town.
He was eventually diagnosed with anxiety, attention deficit hyperactivity disorder (ADHD), opposition defiance disorder and some bipolar tendencies, which "opened the door for services," Thunker said.
But she said the family nearly had to give up custody of Ned to the state to get the care he needed.
The National Institute of Mental Health reports that about 26 percent of the general population has sufficient symptoms to be diagnosed with a mental health disorder.
About half of all lifetime cases of mental illness begin at by the age of 14, and decades often lapse before these people get treatment, according to research supported by the NIMH. By the time they reach adulthood, their disorders are more severe and not as easy to treat, leading to the development of co-occurring conditions, research finds.
But knowing when social awkwardness is a personality disorder that might lead to violence is hard to predict, say psychologists. And often the signs aren't as pronounced as they were in the Thunker family.
"We have learned whether or not they have a diagnosable disorder, there are precursors or signs going on," said Kenneth Dodge, director of public policy at the Center for Child and Family Policy at Duke University.
"But these single events [like the Sandy Hook massacre] are very difficult to predict and we don't want to beat ourselves and our neighbors up that we didn't discover it or know it ahead of time," he said
Susan Klebold, whose son Dylan, with Eric Harris, slaughtered 13 students and teachers at Columbine High School in 1999, said she missed many signs of his depression and suicidal thoughts.
In a 2009 article in Oprah magazine, she wrote about Dylan as a joyful child who grew less confident and more shy -- "uncomfortable when he was the center of attention." By senior year, he was quieter, and she later learned through his journal writings, "expressing profound alienation."
"It never occurred to me that the gravest danger -- to him and, as it turned out, to so many others -- might come from within," she wrote.
"I think I believed that if I loved someone as deeply as I loved him, I would know if he were in trouble," she said. "My maternal instincts would keep him safe. But I didn't know. And my instincts weren't enough. And the fact that I never saw tragedy coming is still almost inconceivable to me."
Dr. Robert Golenbock, a pediatrician who lives in Newtown, Conn., lost a 6-year-old patient who was killed in the Sandy Hook shootings. He, too, is concerned about the resources parents have to deal with a mentally ill child.
"When a child is 2 and they look sick, you can pick them up and take them to the doctor," Golenbock said. "And when they don't want a shot, you can hold them down. But when they are 16 or 17 or 18, you've got a problem. They are not willing participants. Sometimes you have to call the police or drive to get them to the hospital for crisis intervention."
Older children can be prescribed medications, but they don't always take them. Seeing a psychiatrist can be expensive and many parents don't have the financial resources to pay for private care.
"There isn't a good system," he said.
Sometimes parents must abandon their legal rights so that the child is a ward of the state and can get free residential treatment.
In a posting that went viral this week on the Internet, Liza Long wrote in a blog, "I am Adam Lanza's Mother," about her son's violent threats. "I love my son," she writes. "But he terrifies me."
She said she had her son taken to the hospital by police when he threatened her with a knife after an argument over what color pants to wear to school -- not the first incident.
Psychologist Dodge said handling belligerent and troubled children is "very distressing" for parents, who have high hopes that their child will grow up to be a success in school and in life.
"But in elementary school, they are difficult with their peers and have conflicts," he said. "There is trouble at home and more conflicts. Middle school it escalates and is very taxing on parents. For some kids, by the time they become a teen, they are so alienated from their families that it snowballs and their parents give up on them."
He acknowledges that mental health resources are underfunded and schools must do a better job of providing resources for families. And parents also should reach out for help.
"Talk to a school counselor. Talk to the child's pediatrician. Talk to a community resource," he said. "Don't go it alone. Too many mothers and fathers are uncomfortable or hope the child will grow out of it and don't access resources."
Mary Thunker agrees that parents should have a "loud voice," when advocating for their children. Her daughter, who was divorced, moved in with her when Ned's violent behavior escalated.
"Ned was aggressive and more than any one parent could handle and the four others need attention, so we all worked together," Thunker said. His younger brother was also starting to show signs of a milder form of oppositional defiance disorder.
In 2009, when Ned was 12, his behavior problems came to a head and although his doctors said the boy needed "more than a year" of expensive residential care, the state denied payment, according to Thunker.
"The doctors knew that the only way to get services in the time frame was to give up custody and let him be a ward of the state," she said. "I came unglued and said, 'We are never doing that.'"
The family kept appealing the state's decision and eventually got a state senator to intervene. Ned won his appeal and was sent to Boys Town, the Catholic institution of film-fame that takes in troubled youth.
The family moved 150 miles from home to Omaha to be closer to him and to stay involved in his treatment. He stayed 22 months.
"We really worked to educate ourselves," said Thunker, who has since become an advocate for the mentally ill and helped pass legislation to make it easier for Nebraska parents to access health care. Her daughter now helps parents navigate services.
"Most families don't realize there is help to be had," she said. "We had to fight really hard to get medical care."
Her advice to other parents: "Don't ever give up."
Today, Ned is back at home, on a medication regimen and in therapy.
"He's doing well," his grandmother said. "I am not saying every day is a picnic, but the bad days are less frequent and less severe. We no longer think he is a safety risk."