MIAMI — Bidding in an online auction for the pistol former neighborhood watch volunteer George Zimmerman used to kill Trayvon Martin had gone well into the millions by this morning, though it was unclear if they were serious bids.

The website for United Gun Group began hosting the auction Thursday after another website, GunBroker.com, took down the auction saying it wanted “no part in the listing on our website or in any of the publicity it is receiving.”

Hours later, United Gun Group tweeted that it would post Zimmerman’s ad. The new link was posted, along with a statement from Zimmerman. The site calls itself a “social marketplace for the firearms community.”

Bidding on the 9 mm Kel-Tec PF-9 pistol began at $5,000. By Friday morning, the site showed bidding had surpassed $65 million. But the site also showed that the account of the leading bidder — who used the screen name “Racist McShootface” — had been deleted.

Critics called the auction an insensitive move to profit from the slaying.

Zimmerman had told Orlando, Fla., TV station WOFL that the pistol was returned to him by the U.S. Justice Department, which took it after he was acquitted in Martin’s 2012 shooting death.