A cop who just received a course on violence is less likely to pull the trigger of his gun. Research has shown that many officers never pull the trigger for self-defense in their entire career. One major effect from critical incidents and from violence is post-traumatic stress disorder. Officers can become moody and irrational. Many have trouble sleeping and behaviors change.
Some people stop eating, while others pick up old habits such as smoking and drinking.
I was about half-asleep. I don't know what I was looking for, but on my way through the house I cocked my weapon. On the way through the house, the .357 discharged and shot a hole through my floor. These are real problems that effect not only the person living through it, but their family as well. The APA web site lays out many of the symptoms of post-traumatic stress.