[MI] complaint about manager

Complaint

I have a question regarding a complaint made. So a complaint was made against someone who is a manager. The complaint made was by a person who was removed as a supervisor of one department for making people uncomfortable but he claimed he was being bullied and cried. They put him in our department and recently he has done some weird things like say he was gonna buy someone something and then didn’t do it and just never returned back to that. He has gone silent on everyone around him.

Recently he apparently filed a complaint about the manager above him and we don’t know what was said but now her job is on the line and she has been completely separated from the team she was once over seeing. Only thing we know is that he said she was not speaking to him professionally. Most conversations happened through zoom and text. If it is in regards to phone calls how can they go by his words about phone calls? Would that not be hear say?

Also, is the manager able to find out from HR what was said about her and can she rebuttal it in anyway? I am confused how he is manipulating everyone. Any help is appreciated