Ok please tell me if I did this right.?

I followed all the steps on the R 134a can of refrigerant for my ac. I attached it to the low compressor. then turned on the car put the ac on high and then turned the valve to release it into the car's ac. after about 10 minutes I noticed that the needle on the gage was pointed all the way to the red and the car began to blow hot air instead of cold air. Obviously something went wrong. And then I remembered that I forgot to shake the can well before I attached it to the compressor. (could that be why?) I don't know but something is not right. When I detached the can, it seemed as it was still full and that nothing came out. What did I do wrong? Should I try it again?