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Dictionary first definition of "Dock"
1.a landing pier.
2.the space or waterway between two piers or wharves, as for receiving a ship while in port.
3.such a waterway, enclosed or open, together...

I am not so sure about that. There is mention of try to use cover fire. So they were shooting through the wall towards the offender but not AT the offender in order to get the offender to "duck" so...