The next time you see him, ask this guy what happened.

当你下次看到他，问一问这家伙，到底发生了什么事情。

youdao

"I almost lost my job today."—"What happened?"—"Oh, I punched out this guy."

“我今天差点丢了工作。”—“怎么回事？” —“噢，我把那个家伙狠揍了一顿。”

《柯林斯英汉双解大词典》

Another source of evidence could of course be to ask the guy, when you see him next, what happened.

另一个证据来源当然可以是，当你下次看到他，问一问这家伙，到底发生了什么事情。

youdao

"It was like a giant jigsaw puzzle and the more we started to unearth and peel back the onion of who this guy was and what happened to him in the past and trying to truly understand the reason why he would be so obsessed with a specific case once we start to uncover these things about him we realized that once we explain one set of circumstances we needed to go even further with another set of circumstances."

VOA: standard.2010.02.27

So now thankfully I found the lightest one which happens to be this guy here and so what's just happened?

现在我找出了最轻的，它就是,这个杯子，那么刚刚发生了什么呢？

哈佛公开课 - 计算机科学课程节选

What happened to the guy who wanted to dump money from helicopters into the waiting arms of consumers below?

FORBES: A Modest Deficit Proposal

My friends back home in Texas were going to ask what happened to the free market guy they knew.

FORBES: Political Gridlock Can Prevent A Quick Solution To The Next Big Crisis

When I was in college and I was young, you read these great novels that have these ambiguous, artsy endings what happened to who, where did the bad guy end up, is the couple staying together?

WSJ: Satirizing the Sunshine State: 'Star Island' by Carl Hiassen