What was he supposed to do?
Titanic was a three screw ship, with the rudder behind the center screw. ( contemporary opinion is that she was WAY under-ruddered). The two outboard engines were reciprocating, exhaust powering the center turbine engine.
What he SHOULD have done , according to the seamanship "bible" published in 1910, was reverse the port engine, full ahead on the starboard.(also applicable to a two-screw ship). It would have kept the turbine running, the center screw working, and the rudder effective.
INSTEAD, he "jammed on the brakes", full reversed both reciprocating engines, which SHUT OFF the center screw, and blocked the rudder from doing much of anything, and........ the ship didn't answer the helm, hit the iceberg and sank.
Oops.
Edit: actually "grazed" the iceberg, put a few small holes in the first five compartments, a couple more than she could have survived
A continuous big gash like most drawings of the Titanic, she would have gone down in ten minutes, not two and a half hours.