Iran shot down spy plane over international waters to interfere with intelligence gathering on their attacks on shipping

Fox News:

The smoke trail of a U.S. Navy drone that was shot out of the sky over the Strait of Hormuz by Iran can be seen in video released by the Pentagon on Thursday as tensions escalated over what military officials described as an "unprovoked attack."

The U.S. Navy RQ-4A Global Hawk, an unmanned aircraft with a wingspan larger than a Boeing 737 jetliner, was brought down by an Iranian Islamic Revolutionary Guard Corps surface-to-air missile that was fired from near Goruk, Iran on Wednesday night, according to Lt. Gen. Joseph Guastella, head of U.S. Air Forces Central Command.

"This was an unprovoked attack on a U.S. surveillance asset that had not violated Iranian airspace at any time during its mission," Guastella said. "This attack is an attempt to disrupt our ability to monitor the area following recent threats to international shipping and free flow of commerce."

The location where the U.S. Navy RQ-4 was downed by a surface to air missile fired by Iran, according to U.S. military officials. (Department of Defense)

Guastella said at the time it was struck by the missile, the drone was operating at a "high-altitude" approximately 34 kilometers from the nearest point of land on the Iranian coast.
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There is a video at the link above. 

This report seems consistent with what I surmised had happened earlier and is also consistent with the reasons I thought Iran shot it down.  I think an appropriate response would be to attack all of the missle launch sites Iran has in the area.