A recent deadly shooting of an innocent man by Denver cops has sparked a disturbing reaction: An unknown group has passed out fliers promising hefty rewards for a police officer’s life.

The fliers, placed under car windshields and discovered Tuesday morning, offer $5,000 for a “crooked cop’s life” and $10,000 for a badge. They’re signed by a group called “N.E.F.F.” but are missing a phone number.

Pictured on the handouts is 63-year-old Frank Lobato (search), a disabled man shot and killed July 11 by police officer Ranjan Ford Jr. (search) The officer, who was responding to a domestic violence call, mistook a soda can in Lobato’s hand for a gun.

Denver police are being watched closely these days because of 11 fatal shootings in 16 months — including that of a developmentally disabled 15-year-old boy, Paul Childs, whose face is also on the fliers along with Lobato’s.

The Denver Police Department (search) is taking the threats very seriously, and has put patrol officers on alert. The perpetrator faces a felony charge: criminal solicitation for murder.

Click on the video box near the top of this story to watch a report by FOX News' Carol McKinley.