When your Superior Starts to use abusive language/Bashing, call 999, and if possible make a Video as well, it would be considered as a Proof & Witnesses Should not back out, usually have seen ample of times when the Case is Legitimate but at the End Witnesses Back out....

Legally, Police will handover the Investigation to CID, & then CID would start taking the Interviews of the Witnesses & any evidence related to the Crime as well...