9th June 2018 From India, Mumbai
This is in addition to what senior member of this forum KK!HR has said. Abuse is a result of either frustration or conflict. So what exactly happened? Who were the witnesses? Have you taken the statements from the witnesses?
In fact, your post is little misplaced. If some employee abuses HR Head, then why HR Head is unable to handle the situation on his/her own? Why you or HR Head is looking for advice on this forum? In fact when query like this appears on the forum, it is HR Head is supposed to guide. However, what we are observing is complete contrast!
9th June 2018 From India, Bangalore