The mouse was already dead once the first fiftieth a second when the blender turned on. Probably less, since it's running at about 700RPM. Quick and painless.
Plus, mice die every day. Between snakes and other predators eating them, which is much more painful, and mouse traps, which snap a mouse's neck, and sometimes fails and traps them until they die of blood loss or hunger. Those mouse traps you probably have in your bathroom closet would probably be more painful than that.