"Nur had commissioned him to kill 16 Americans supposedly responsible for airstrikes on ISIS in Kobane, Syria. ISIS had come up with the names and addresses of the pilots by hacking a military database. Omar complained this information was too "hot": He had accidentally clicked on the link to the names and addresses, making it possible for law enforcement to track him."
http://www.weeklystandard.com/minnesota-men-on-trial/article/2002781