Factual error: The bus that Edward stabs has an NYC Transit X90 route marker on it. This route does not go through Times Square.
Continuity mistake: When Nathaniel leaves the hotel room after he hangs Pip in the closet, there is a window shot of him crossing the street and heading to a snow covered sidewalk the next day. But when Pip frees himself and runs outside, there is no snow.
Continuity mistake: When Edward stabs the bus, the length of his sword is inconsistent. For it to reach all the way down as far as it did (as seen from inside the bus), it would have to be much longer than it is throughout the rest of the movie.
Answer: If Elsa died from magic, her son, the prince, would know and turn against her. If she died by somebody else or a tragic accident, the Queen's hands would be clean.