Kevin C. Downs for NY Post A late night argument outside a Manhattan deli turned deadly on Saturday– leaving one man shot dead and another wounded, cops and sources said.  Gunfire erupted at the intersection of Avenue B and East 13th Street in Alphabet City around 11:38 p.m., striking two 28-year-old men in the abdomen, cops said. “I was making the pizza and I heard a ‘pop’ and then after a while another ‘pop,’” an employee at nearby Pop’s Pizza told the Post.  Gunfire erupted at the intersection of Avenue B and East 13th Street in Alphabet City around 11:38 p.m., striking two 28-year-old men in the abdomen, cops said. Kevin C. Downs for NY Post “One guy walked up the block, holding his belly, and sat down right here,” the pizza chef said, pointing to a small bench in front of the store.…