2009 Chevrolet Impala engine problems

Stopped at the top of a snow covered hill. Put the transmission in 2nd gear and proceeded down the hill. The vehicle got up to about 15 MPH then lost all power; engine quit, no brakes, and the steering wheel locked in place. Because the brakes were not working the vehicle gained significant speed going downhill. Not being able to steer the vehicle because the steering wheel was locked it went off the road and hit a tree. Upon impact the air bags did not deploy.

On my commute to work on the interstate my impala shut itself off. I was in the left lane when the car showed the reduced engine power on the information panel, it then fully disengaged all engine power and powersteering. Being in the outside lane I had to maneuver my impala through the heavy traffic and almost caused numerous accidents trying to squeeze to the shoulder. I then coasted off into the grass almost into a large ditch but I slammed on the brakes hard and went into a skid coming to a full stop.