A) Is it legal for a broker to monitor that their customer is about to place a large size order (i.e. it was to sell 4k shares at a 500 share bid), and to quickly sell the 500 shares themselves instead of the customer?
B) Possiblity 2: the bid of 500 shares was on ARCA, the broker sent his sell order on CINN, and maybe it wasn't the broker, but some other party--but either way, something not handled well by the broker.
B) Possiblity 2: the bid of 500 shares was on ARCA, the broker sent his sell order on CINN, and maybe it wasn't the broker, but some other party--but either way, something not handled well by the broker.