While flying in a park in the centre of a town today I suffered my first fly away. I was in GPS mode, I went up to about 30 feet then I lost control over it, it shot up to over the height of a very large oak tree and went off over the town, it was a very frightening experience! I panicked, pulled the sticks back and forward but I had totally lost any control of it. Thankfully I remembered to switch to atti mode, I was able to regain control over it and got it back roughly over the park but it was flying very erratically, much faster than I would have expected under the conditions. Simply to get it down, I crashed it to the grass in the park. Apart from a damaged blade, it seems fine. When I got home, I plugged it into Naza and it told me the GPS needed calibrated which I have done. I had a short test flight and all seems to be fine with it. I should say, I had struggled to get no red lights while waiting so I flew it with 2 flashing lights which I was of the impression was sufficient for gaps flight. I have vowed to practice atti mode flying now. Any thoughts on any of the above, advice for the future maybe?