Over at the Chicago Reader, Steve Bogira flagged something remarkable in the report from Jason Van Dyke's shooting of Lacquan McDonald:

Van Dyke also said he recalled a previously issued Chicago Police Department bulletin warning of a weapon which appeared to be a knife but which was actually capable of firing a bullet, making it a firearm.

"A search of CPD records showed that a safety bulletin was indeed issued to officers in December 2012," Bogira writes, "warning them of a 'revolver knife'" capable of firing .22-caliber cartridges.

While it sounds like something in the SkyMall catalog Charon gives you on the way to hell, there is in fact a .22-caliber revolver knife in existence.

Or, rather, was. The G.R.A.D. RS 1 knife gun—illegal in Chicago even after the handgun ownership ban fell in 2010—was a boutique device that fires six short .22 rounds. The CPD didn't get back to Bogira on whether one had ever been used or recovered in Chicago, but the odds seem awfully slim: According to Guns.com, less than a thousand were made from the 1990s to when the company folded in 2007, starting at $699 for the base model and rising to $1,999 for the "gold-plated series." As a result, they're now very expensive—when Rock Island Auction Company put one up for bid in 2011, they estimated it would go for $1,500-$3,000.

If you want to go the retro route, buy local, and don't mind some elbow grease, the market for a Huntsman one-round jackknife pistol, manufactured by Chicago's U.S. Small Arms Co. in the early 20th century, seems to be more reasonable.