Engine shut off while running, losing compression in three cylinders

There are many possible reasons for losing compression of the cylinders and if they are on the same bank, a skipped timing belt is the most likely cause.
Check the timing belt condition and verify if the marks are aligned correctly.
The other possible cause is overheating resulting in a bad gasket. This engine is notorious for failed head gaskets and coolant getting to the cylinders.
Have the above checked first.