In my experience, it comes down to matching patterns.
Here's what I think likely happened: your friend talked to other people who went through tragedy. He noticed something common in their behavior. It can be something so subtle that it's invisible to most people, but your friend notices these kind of things. Then when he talked to the current person, he found the similar pattern.
Here's what I think likely happened: your friend talked to other people who went through tragedy. He noticed something common in their behavior. It can be something so subtle that it's invisible to most people, but your friend notices these kind of things. Then when he talked to the current person, he found the similar pattern.