PHILADELPHIA (AP) – Instead of a gun, convenience store clerks have been attacked with fiery hot drinks in a series of recent robberies, police said.

Typically, one of the robbers buys a coffee or hot chocolate and throws the drink in the cashier’s face while his accomplice scoops the money from the till, city police Sgt. D.F. Pace said Monday.

At least one cashier has suffered third-degree burns in the splash-and-grab robberies that began about two weeks ago, Pace said.

The pair, repeatedly caught on surveillance cameras, have robbed six convenience stores in New Jersey, three in Philadelphia, five in Delaware County, one in Bucks County and one in Wilmington, Del., police said.

“In my 37 years of reading police reports, and studying criminals and crime, I have never heard of something like this,” said Lawrence W. Sherman, director of the Jerry Lee Center of Criminology at the University of Pennsylvania.

Wawa and 7-Eleven, primary targets of the pair, are offering up to $10,000 for their arrest.