Bullet casings from the brazen killing of UnitedHealthcare CEO Brian Thompson in midtown Manhattan bore the words “deny,” “defend” and “stop,” NBC News reported Thursday, citing law enforcement sources.

These chilling words echo the title of a 2010 book, “Delay Deny Defend,” whose subtitle is “Why Insurance Companies Don’t Pay Claims and What You Can Do About It.”

Thompson’s Company, a subdivision of UnitedHealth Groupis the largest private health insurance payer in the United States and has been the subject of heated controversy over its relatively high denial rate of health care claims.

Thompson, 50, was shot dead early Wednesday morning outside the downtown Hilton Hotel by a masked gunman with a pistol with a silencer. The shooter remains at large after escaping on his bicycle into nearby Central Park.

Thompson, a married father of two sons, was about to enter the hotel on West 54th Street near Sixth Avenue for a UnitedHealth investor meeting when he was fatally shot.

Three spent bullet casings and three live cartridges were found at the scene.

This is developing news. Check back for updates.