They were leaving, using the pathway; if you noticed, they are in a decent neighborhood and some people find it mildly disrespectful for others to walk on their grass.

Backing away and asking them to leave is one thing, but to jump to grabbing a taser, that by law can be considered a deadly weapon, and not the brightest idea to brandish for an exaggerated reason, is a bit much.

Would I get a little anxious about some strangers dressed up asking for candy- even if I had Halloween decor outside? Sure, but I would be a little more restrained (as I have been in different run ins) and not go for the nearest weapon and brandish it while they are attempting to leave the property through the only available pathway, trying to- in their view- be respectful of the property.