- Alcohol and drug use
- Addiction to media products
- Fascination with weapons and violence
- Experience with guns
- Access to guns
- Sullen, Angry, Depressed (SAD)
- Seeking status and worth through violence
- Threats (of violence or suicide)
- Chronic anger
Most of these are self-explanatory but I want to add a couple of brief elaborations: Note that alcohol and drug abuse are at the top of the list; one recent study shows that an astonishing 75 percent of homicides by young people occur when they are high or drunk. Next, the term SAD is used by my firm's behavioral scientists for easy identification of Sullenness, Anger, and Depression, which include changes in weight, irritability, suicidal references, hopelessness, and loss of interest in previously enjoyable activities.
I don't imagine that the items on the list above apply to your sons. Also, there are seven key abilities human beings need to effectively manage life: the ability to motivate ourselves, to persist against frustration, to delay gratification, to regulate moods, to hope, to empathize, and to control impulse. Many of those who commit extreme acts of violence never learned these skills, but I expect your sons have.
If you are still worried, let me know.