Altadena, California Saturday 17th November 2012, 4:00 PM:

Two OH-58 Helicopters have collided during departure/arrival operations at/over the Pasadena PD Helipad.

[Picture - CBS 8]

4 crew members and 2 people on the ground were injured during the collision, which left both helicopters badly damaged but remaining upright on their skids. Footage shows both helicopters lost their main rotor systems.

Link - CBC Los Angeles:
http://losangeles.cbslocal.com/2012/11/17/6-reportedly-injured-after-2-pasadena-police-choppers-collide-in-altadena/#.UKg-rUjRgtk.twitter