How to Ask 'What Happened?' in English

What's the best way to ask 'What happened?' in English? You can simply say 'What happened?' but there are also many other ways to ask this question depending on the situation. For example, if you're trying to be polite, you could say 'What seems to be the problem?' or 'Is everything alright?' If you're trying to get more information, you could say 'Can you tell me what happened?' or 'What's going on?'