Brake Fluid Leak

Ok I changed my front brakes and, i think I may have screwed up cause when I was pushing the calipars down. I dont know If I were to do something else 1st. But changed the front brakes and added brake fluid and within like 10-15 minutes maybe all the fluid is leaking out of the rear end. Havent seen the truck until tonight, But any suggestions b4 I get home, what this could be?

FIXED: Wheel Cyclinder went bad, part is like 13-19 bucks at Advance autoparts. But be prepared to buy rear brake drums. If the cyclinder goes bad, then most likely your brakes are done as well.