George Zimmerman, the neighbourhood watch volunteer who killed Trayvon Martin, is to auction the gun he used to shoot the unarmed teenager.
Zimmerman shot and killed the 17-year-old after a violent altercation in Florida in February 2012.
He was cleared of murder after arguing that he acted in self-defence.
His acquittal led to nationwide protests over race and gun control, and the start of the Black Lives Matter movement.
Zimmerman has now placed the 9mm handgun on online auction site, GunBroker.com, with bids starting at $5,000 (£3,500) after it was handed back by the Department of Justice.
He told potential buyers that it is an "opportunity to own a piece of American history".
He said the firearm was "used to defend my life and end the brutal attack from Trayvon Martin”.
Proceeds from the sale will be used to fight "BLM [Black Lives Matter] violence against Law Enforcement officers” and "Hillary Clinton’s anti-firearm rhetoric”, he said.
Trayvon Martin's family said they would not "comment on the actions of that person".
Defending the move to put the gun up for sale, Zimmerman told local media that he could "do what I want with my possessions".
"What I've decided to do is not cower," he told a Fox News affiliate.
"I'm a free American. I can do what I want with my possessions."