“President Barack Obama and his national security team knew they had to stop the advance, and they knew that any military action would put at risk the lives of at least four Americans being held by the group in Syria. One after another the American hostages — James Foley, Steven Sotloff and Peter Kassig — were murdered. The fourth, Kayla Mueller, was killed in 2015.”
Source: US adjusts policy toward hostages and their families – U.S. – Stripes