Depends on the severity. But counseling is a good place to start.
The issue is... And this is something I have witnessed in person being in the emergency services... You don't know if someone will be affected by something like this until.. Well. They are affected by it. - People can go decades seeing horrible stuff and eventually just break almost at random, you cannot predict it. Seriously.
We aren't just talking about computer generated images here either you know, these people are seeing some horrific stuff in the name of "research" for our entertainment.
Give them some support... It doesn't have to be expensive, time consuming or whatever... Just someone they can talk to and refer them to other support services.
That's strange to say: "at random",maybe for the people around them but they themselves must have had a lot of stress to eventually break from it and sometimes people also force themselves into those bad situations because they feel trapped.
When I say at "random" I mean there is no predictable time frame when someone will get PTSD.