Overheating Mustang

My son has a 2005 mustang 6 cln. He pulled into our driveway and shut off his car and smoke came out of his hood. As he opened the hood a liquid sprayed out all over the engine compartment. I squeezed the bottom radiator hose and it was very supple, not solid. All hoses were like this. My son started the car and a hissing sound came from the thermostat area. I removed the hoses, one. The top one was partially bulged, I removed the thermostat and behind it, on top of the engine compartment was covered with a thin oily fluid that was dark and on the side of the thermostat was a build up of waste where it appeared that there was a leak of some type, but no hole was found. I inspected the O-Ring and it appeared in good condition. There was a large amount of water in the bottom of the hose that came out when I removed it. Water came out under pressure and very hot. Question? Can the O-Ring blow and not show damage when there is residue on the outside of housing? Can I reuse the housing if the O-Ring is the fault? What could be the cause of the oily fluid on the top of engine? I am not a back yard mechanic just trying to help my son. Any idea's. Thank you.