 He worked at a nursing center, and we've learned he was a member of a local gun club. Former classmates say he stayed to himself. CBS News national security contributor Samantha Vinograd. Lone actors are notoriously hard to detect and hard to prevent from engaging in violent activity. They typically don't talk to other people, so it is harder to detect an individual who isn't in communication with others. A former Marine vet and volunteer firefighter was killed at the rally. Two who were wounded are in stable condition.