PITTSBURGH — Pittsburgh police are trying to stop some robbery suspects from doing the “monster mask.”

Police say three drivers — two delivering pizzas and one delivering Chinese food — have been robbed since Nov. 23.

The first heist happened when a driver was called back to a residence where he had delivered food earlier, albeit from a different phone. The next was Nov. 27. The last heist was Sunday when a gunman wearing a Freddy Krueger mask from the “Nightmare on Elm Street” movies and another in a black ski mask robbed a driver.