Cruise Control problems of the 2013 Cadillac SRX

This is a report of a nearly fatal accident on June 29th, 2013 with a new Cadillac Srx that was leased from gm. The accident involved both me and my daughter who were belted in the vehicle which caught fire and accelerate to 110 mph. We were traveling on rt 127 n with the cruise control set at 60 mph. I was passing another vehicle and the speed started to dramatically increase. I would break and the speed would come down and then it would continue to rise. Black smoke was coming out of the engine. Using both feet on the brake, it finally came down to 5mph, but it would not stop. I pulled over at 5 mph and shifted the car into park. I used onstar and shortly thereafter the fire department, the sheriff, and another police officer were on the scene. This was a life threatening event!! the car was towed back to the dealership in adrian. I leased this car on 5-31-13, our second Srx and less than a month old. I sent a letter to dan akerson at gm regarding the aforementioned and have had no response. I am going on week two with no car and no resolution with this incident.