Many Veterans don’t show any signs of an urge to harm themselves before doing so, but some may show signs of depression, anxiety, low self-esteem, or hopelessness.  They might also seem sad, depressed, or agitated most of the time.
and acting differently is a sign that something might be up?
Yes, they may change the way the act . They might start to do poorly in work or school and they might act violently or take risks
is there any place that I can go online to read more on this?