Police are racing to catch the killer of 15 flamingos at the Frankfurt Zoo, where the creatures were beheaded over the space of two nights. The zoo director said Monday that autopsies were underway to figure out how the Chilean flamingos were killed. He also said the killer may have been human, because even though bite marks were found, they may have happened when the birds were already dead. Even though extra security was put in place after the first attack, the second went unstopped. Part of the problem, said the director, may be that flamingos don't cry for help when attacked.