Questions in the Connecticut school shooting are turning to the mental state of the 20-year-old shooter.
Did Adam Lanza show warning signs of mental illness? Was there anything that could have been done to prevent the tragedy?
Descriptions of Lanza, such as "he was quiet" and "he kept to himself," are similar to so many heard before in other mass killing sprees.
Local mental health experts described the warning signs to look out for.
"They may be a bully on the playground, they may be cruel to their classmates, they may hurt animals at home, they may be involved with blood and gore and games that depict violence," said Tracy Riley, a licensed clinical social worker.
Other factors to look out for include someone who is socially withdrawn, isolated, doesn't want to maintain friendships with their peers, and has high self-esteem, not low.
Riley, who specializes in treating children and young adults, says believe it or not, thinking about suicide or homicide can be relatively normal, anything beyond that is not.
"It's when they have a plan and an intent to act on that plan that people need to become aware of it," Riley said.
What happens when teachers or parents, even friends, become aware that someone might act violently? What can they do?
"Unless and until the person has been diagnosed with a mental illness and presents himself or herself as a danger to themselves or others, there's no reason to Baker Act them," said William Devereux, a licensed clinical psychologist and attorney.
Devereux said that's why it's so important to keep a closer eye on others, pay attention to any potential warning signs, and have an open dialogue with friends and loved ones.
They are seemingly easy steps that could help prevent the unthinkable.
"The person in a deep, deep depression that becomes delusional and psychotic, they're seeing something else in the world," Devereux said. "They're not understanding the world, and it makes sense to them, and because it makes sense to them, they can act on it."