Refrigerant is spewing out when air is on

I just got this car 2012 prius from my sister so I don't know when or exactly how it started. She said the ac was only working sometimes and I would assume she had the air on trying to get it to work many times. But I just turned it on and have found out that when the air is on I hear a sound that sounds like the fan is turning on, getting really fast, and hitting something. Then it stops and repeats in bursts. I checked and refrigerant is spewing out of the ac when this happens. It doesn't matter if the ac is on or not. This problem occurs whenever the air is on. Any ideas as to what is happening?