1996 Dodge Caravan Losing Break Fluid

My van had been driving completely fine and the other day I went to slow down and it felt like I had NO breaks. Then a couple of days went by where It was difficult to use the breaks and I pretty much had to put the brake to the floor to stop. THen the brake light came on. My husband checked the brake fluid and said it was low so he filled it. He then drove 22 miles came home and said the breaks were still aweful so he picked up some pads. He checked the fluid and it was empty after only driving the 22 miles. He found a little box spraying out break fluid? Any idea what this little box may be? He said he has never seen one before?

Thanks!