What it sounds like to me is, you had a blown head gasket. The coolant got into at least one cylinder, and this caused the piston to blow. air will compress on the compression stroke, but coolant will not, and the pressure has to go somewhere. once the piston was blown, the coolant went into the pan, and was circulated with the oil and piston parts. In addition, the head gasket was further damaged, and if valves were also damaged which is likely, coolant and or oil could well have been blown back through the intake manifold and up the carburator (if it is a carburated engine) or if a fuel injector was blown out too, into the air intake filter. Once an engine starts to come apart when running at speed, there can be a long train of damage such as you describe.