The tube from the radiator to the engine broke off.
The radiator is connected to the engine via a rubber hose. The most common issue is the hose being old and rotted. If this happens it can burst or develop a slit that can look like a break. The repair is to simply replace the radiator hose. This is a repair that should be taken care off as soon as possible to avoid overheating the vehicle. Overheating can cause secondary damage, like blown head gaskets, that make the repair significantly more complicated.