Check Engine Light On problems of the 2014 Mazda CX9

I was slowly approaching a stop light when our 2014 Mazda cx-9 started having vibrations, which at first came from underneath, between the driver's row and the 2nd row passenger. It immediately felt as if the car's engine was about to fail. I managed to make that right turn, carefully stepping on the brakes, and crossed a rail-road crossing. The car was running at a speed of 20 mph. I slowed down to make another right turn towards my destination, then the engine abruptly died. The battery and check engine lights suddenly lit up on the dashboard. From the intersection's stop light to the location where the engine failed, it was a distance of approximately 0. 5 mile. My wife came and picked up our 3 children from the corner of the street. My brother-in-law came to my location with jumper cables and gave my engine's battery a jump-start. The engine started but the vibrations were stronger. The car ran for another 0. 3 mile before it died again. I had the car towed to the Mazda dealership from where I purchased the car. After 1 day I was told that the incident was possibly due to a bad tank of gas. Another day later, I was told that something else was wrong with the engine, and that it was unrelated to the earlier suspicion of bad gas. After 5 business days, I was told that the engine's cylinder 6 needs a new cylinder head. The other option was a complete engine overhaul. The car has never been in an accident, and has approximately 81,000 mileage. The estimated cost for repairs was $5,834. This is a very serious safety issue that warrants an investigation. Had the car experienced engine failure on a busy interstate, my family and others could've been seriously injured or even killed.