Trump says Iran downed US Apache helicopter, response is 'of necessity'

President Donald Trump said Tuesday the Iranians shot down the U.S. Apache helicopter that fell overnight near the Strait of Hormuz and is calling for a response. 

"I have just been informed by our Great Military that last night the Iranians shot down one of our highly sophisticated Apache Helicopters while patrolling over the Strait of Hormuz," Trump said in a post on Truth Social. 

Earlier Tuesday there had been some uncertainty about whether mechanical problems caused the crash or an attack. Both pilots of the aircraft, Trump said, were rescued and unharmed, but he said that the U.S. must "of necessity" respond to the attack. 

Two senior officials told Fox News that the U.S. is still investigating whether the Iranians meant to hit the helicopter.

This is the first Apache helicopter known to be lost in the conflict with Iran.