What's behind the selloff in gold and silver?

From youtube.com/markets

Gold extended losses in a choppy session, after suffering the worst rout in over 12 years on Tuesday on concerns its rally had run too far, too fast. Spot gold slid below $4,020 an ounce as US trading got underway, after swings that saw it slump almost 3% earlier and then recover. Bloomberg's Mike McGlone reports.