My coworker went to HR and I don't know what to do?

If you did nothing wrong then there is no problem. The first thing you do is when you go in you politely say "you wanted to see me?". But when you get down to business make sure you bring a pen and a notepad with you and let them do all the talking without getting defensive. When they are finished refer to your notes and find out who filed the report and why. Body language tends to cause suspicion so keep your head down and document what is important and stay calm
Sometimes when you ignore things they do in fact just go away.
Seems like you should just be brave or whatever and tell HR what you know.
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Just be honest with them and tell them what you know. They just want to check the veracity of each parties claim's.
No, you can't ignore HR. They know where you live.
What happened to your coworker?
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