Actually, Moses did murder a guy. That's a fact, and I will support it.
Murder is a legal term, where killing is not. That is why soldiers are not murderers. They are following the laws of the land, and so their killing is not unallowed and is not murder.
Moses was a murderer. He obviously broke a law, because he buried the body and ran away for good. The slave driver was not breaking any laws. He was allowed to beat the slave, and Moses understood this because when he was put in charge, he let owners beat their slaves quite brutaly. He allowed owners to rape their slaves, break up their families, and do many other things that would be a felony if done to a free person, but only misdemeanors when carried out against slaves.
Moses had been adopted by the Pharoah's daughter. He had protection on some pretty high ground, but he still needed to run and hide. That's because he was a murderer, a coward, and he didn't trust that his station would get him off the hook. He killed someone for doing something that it was legal and expected for them to do---so he is a murderer. It's like when a nutjob shoots and abortion doctor. They are murderers, regardless of what they think of the doctor. Because the doctor was operating within the realm of law, and the shooter is not.
None of this means I condone any of what was happening, but when we look at the legal structure, then it is absolutely clear that Moses was a murderer and a coward that ran away instead of sticking around to explain why he murdered some guy for doing his job. And it would have been a pretty weak defense considering that in just a few years, he would be writing out his own law that allowed owners to beat slaves nearly to death----or to a long and drawn out death---but a quick death would have been illegal.