On April 5, 2017, Mattis called the Khan Shaykhun chemical attack "a heinous act," and said it would be treated accordingly. On April 10 Mattis warned the Syrian government against using chemical weapons again. The following day, Mattis gave his first Pentagon news conference since becoming secretary of defense, saying ISIL's defeat remained "our priority," and the Syrian government would pay a "very, very stiff price" for further usage of chemical weapons. On April 21 Mattis said Syria still had chemical weapons and was in violation of United Nations Security Council resolutions. According to investigative journalist Bob Woodward, Trump ordered Mattis to assassinate Assad, but Mattis refused. On May 8 Mattis told reporters details of the proposed Syrian safe zones were "all in process right now" and the United States was involved with configuring them.