Often we're so surprised when a first responder takes their life. They show no signs of struggle or of the pain they're in. I know what it's like because I was there once myself. We're afraid that others will perceive us as being weak and we get very good at hiding our torment and agony from our family and co-workers. I call this the 'false okay' and have created a few images portraying this state of mind.
Here are a few signs and symptoms that may be a clue that things aren't as okay as they seem:
-Loss of interest in activities they used to enjoy
-Withdrawn and distant
-Irritable behaviour, angry outburst, or acting aggressively
-Taking too many risks or doing things that could cause them harm
-Being jumpy or easily startled
The next first responder suicide may be closer to home than you think. I think it's worth the risk to ask a co-worker or family member if they're okay - and when they undoubtedly say "I'm fine" - ask them again but look them in the eye and tell them why you're asking. Give examples of the changes in behaviour that you've noticed. Tell them it's okay, and you will listen if/when they want to talk. Comfort will come from feeling accepted and engaged so offer to just hang out if they're not ready to talk. Here's a good article on how to help someone with PTSD from helpguid.org https://www.helpguide.org/articles/ptsd-trauma/helping-someone-with-ptsd.htm