A Brinks employee opened fire on two armed men who tried to rob his armored truck while he was making a delivery around 11:30 a.m. Tuesday on the 8200 block of Castor Avenue in Philadelphia’s Rhawnhurst neighborhood, police said. The suspects fled north in a newer-model black Nissan sedan with tinted windows and black rims. Investigators recovered eight spent shell casings at the scene; no injuries were reported. The Philadelphia Police Department and an FBI task force are searching for the two suspects, whose images were captured on surveillance cameras. Authorities said the attempted heist is the fourth attack on an armored vehicle in the city in less than a month, including robberies on June 21, June 26 and July 2. Officials are examining whether the cases are connected.