Things could be coming to a bloody head on Friday in Syria. The largest city in the country and the site of recent heavy fighting between government forces and rebels trying to oust President Bashar al-Assad, Aleppo is bracing for a brutal counterattack from the government after rebels captured parts of the city. At least a dozen people were killed Friday morning when government helicopters opened fire, and survivors of the violence are dealing with serious shortages of fuel and food. Meanwhile, 80 tanks are amassed on the southern outskirts of the city, according to a senior rebel leader. “They are preparing to reoccupy neighborhoods taken over by the rebels,” he told The New York Times. A top U.N. official has received unconfirmed reports of human-rights atrocities occurring in the city, including summary executions carried out by both sides.