You may choose to enlist some help in order to intervene. Here are some examples:
This is getting out of hand, we need to step in
This is not right, we need to say something
Watch this short video Group (MP4) for an example of the delegate approach, where you are seeking support from other bystanders.
Tell someone what you witnessed: a line manager, HR, Departmental Administrator, Head of Department.
I’m not sure what was going on but I witnessed this and it made me feel uncomfortable. I thought it was important you knew