Ouch! Similar thing happened with my hexacopter the first time I got it in the air, except mine was mostly due to my ineptitude. It engaged RTH on low battery, as I'd programmed it to, but I didn't realise at the time that the compass wasn't calibrated properly. I totally lost control and it veered away from me before flying straight toward the ground at a fair rate. Snapped the PCB frame and one of the landing gear mounts. That was not a fun day!