Are there any episodes that are about a murder?

Depends on what you mean by "about a murder". If you are asking if the monster ever successfully murdered someone, no. But there are other factors.

First being some villains did do things that could have killed or injured someone in the process of their scheme, but anytime this was on-screen somehow the day is saved.

If the gang finds a place wrecked and somebody missing, typically this is only a kidnapping, that they will discover where the person is or went by the end of the episode.

But the other important factor being, a lot of the weekly monsters have the backstory of being "the ghost of" someone. This pretty much indirectly states someone died as backstory.

As far as "murder" or close to murder ones I can think of:
1. The only one from this series is the Snow Ghost. Which is supposedly the ghost of a Yeti. In the on-screen flashback it chased a man to the point he jumped and landed on a narrow ledge, the yeti tried to follow and fell to his death.

On later series.

2. In the Headless Horsemen episode they lift the backstory out of the Washington Irving story, where the Horsemen dies from having his head shot off by a canon.

3. In To Switch a Witch, the ghost is of a witch from Old Salem. Here backstory being she was burned at the stake.

There might be more, but those are the only ones on the top of my head I remember someone else' actions having a major part of why the person in the backstory is dead.

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