My Manager Just Called Me A "god Damn Sand N****r". What Is My Move?

Location: Georgia, USA.

I work at a chemical plant in Georgia. This happened about 15 minutes ago. He thought he was being funny and everyone around was laughing, from what I believe was out of nervousness and just being stunned, so I laughed it off, too. Now that I'm away from the situation, I'm feeling cut down to size. I've been here over 4 years and he started in October. I feel like I've done a hell of a lot around the plant to earn the respect of my peers and management, while he just throws his weight around as the new plant manager. I have 5 witnesses. What the actual fuck do I do in this situation?

Update: Just got home from work. Everyone who witnessed it said they will back me up. One of the guys is a burly ex-Army dude from Tennessee. Said he's been to Afghanistan and was a character witness for interpreters who successfully gained US citizenship and what the manager said was xenophobic and heinous. Fucking love that guy. Another one is an old head. Been around plants for years. Said either I go to the manager and squash it or be the karma that bites him in the ass. I've chose the latter.

Wrote an email to HR. Their reaction dictates my next move, so I'm playing it by ear. We'll see what happens. I came back to reply to the comments and discovered the post is locked, so please take this update as a token of my gratitude. Reading opinions while stunned helped make my decision and prepare on the situation moving forward. Thank you.