First cut -- Introspection -- and be honest in your evaluation and role you played .. If it is a colleague you can deal amicably and resolve. Escalation is not an immediate (while possible) is not always taken the right away by the Mgmt -- could easily throw it back and say you are not cooperating .. Any how the bottom always who needs who more -- and some places put up or shut up and leave may be a high Road approach but not always appreciated if you were to return to the same company and or similar ones.. It is never pleasant and don't expect the HR / and or any other authority figures to come and bat for you.