Helicopters in formation over Copper

At approximately 3:45 pm 6-16-14 a formation of four helicopters flew over Copperopolis.
At this point the mission is not known.
If you have an idea/ comment please email to coppergazette@gmail.com.

Update:
Many replies identified these helicopters as Blackhawks.

While the mission is still not known the possibility exists that they could have been on a training mission to the Marine Mountain Warfare Training (MMWTC) center in Bridgeport.

Thank you to all who replied with your information.