Trump certainly mocked a disabled reporter, a general, and Ted Cruz by making a particular motion.
It does not seem to be an imitation of his disability though.
1. Serge Kovaleski in motion, not looking like Donald Trump. (starting at 00:30)
2. Donald Trump mocking Ted Cruz the same way.
3. Donald Trump mocking a general the same way, during the same rally.
Note that none of this means that Trump did not treat Kovaleski rudely.