MOSFET shorted after I connect them in parallel, what's wrong?
A pretty normal explanation for this is as follows: -

You said the first MOSFET (on its own) got hot but continued working and my 1st observation is that you may not have been driving the gate "hard" enough. This would have caused some switching losses and possibly some conduction losses causing the device to get hot but it still worked.

So then you put another device in parallel and in doing so you have "shared" the gate drive current - the gate capacitance has effectively doubled and the rise time and fall time of the gate signal has doubled increasing switching losses for the device that begins to turn on first (not all FETs are identical). It rapidly overheats, melts and short circuits.

If you want this confirming, produce a circuit diagram of what you actually did.