Tailkinker

Answer: Try watching a bit more closely. The "guy" in question is Bron, Katrina's would-be suitor, who is pretending to be the headless horseman to make fun of Crane. They're playing a joke on him, nothing more than that.

Tailkinker ★

Answer: The scene happens to be a play on a common theory of how, in the original Legend of Sleepy Hollow, that Brom was pretending to be the Headless Horseman in order to scare Ichabod Crane away from Sleepy Hollow.

Answer: The incentive is the ownership of the lands and property held initially by Peter van Garrett, the older man killed at the start of the film. Van Garrett and his son are killed first, then the widow Winship when it becomes apparent that van Garrett married her, making her a possible inheritor. Once Ichabod arrives in town to investigate, it becomes necessary to remove witnesses to these events, so that they can't give him clues to what's really going on. Jonathan Masbath is killed because he witnessed the marriage and the change of will - he would be able to testify to both. The midwife and her husband were also aware of the situation - due to the widow Winship's pregnancy - so they were eliminated as well (their son was merely in the wrong place at the wrong time). Magistrate Philipse was consulted by the widow regarding the legal status of her unborn child, plus he was actively trying to help Ichabod, so his elimination became necessary. Once the van Garretts were out of the way (plus any inconvenient witnesses), the land now belongs to the van Tassel family. Balthus van Tassel is killed first - Katrina is his first-named heir, with his wife as the second. With Katrina's removal, the wife, Mary, inherits. As she explains in the film, her reason for this is that her family originally lived on the land, only to be evicted. Acting as the van Tassel family nurse, she arranged the death of van Tassel's first wife, Katrina's mother, then seduced Balthus into marrying her, thus placing her in the line of succession - she then proceeds to use the Horseman to eliminate everyone above her in that line.

Tailkinker ★

Answer: Before the magistrate's death, he and the other town elders were arguing and he was packing and seemed to be leaving town, and then being stopped by Ichabod. I like to think that he was trying to escape, and that's why Lady Van Tassel had the Horseman kill him.