At no time during Officer Haygood's WC Testimony does he say he heard Chief Curry's command, "get a man on top of that Triple Underpass.......". Haygood did testify that he saw people on the ground pointing back up to the railroad yard, along with a couple of people being headed back up that way. This prompted Haygood to park his motorcycle at the curb and then run up the grassy knoll toward the railroad yard. This is one of the many reasons that being familiar with Sworn Testimony is important. It prevents Urban Legends from being created and/or passed along.
You are quite correct, Royell.
That was an assumption on my part and should have been stated as such.
Seconds after the shooting, Curry gives the command - "Get a man on top of that triple underpass and see what happened up there".
Haygood has a radio on his bike so can hear the transmission and does exactly what Curry commanded but, as you correctly point out, Haygood never specifically states that this is what happened.
Just to get back to the point of the topic...
...the argument for 'teams' of professionals or multiple professional marksmen often revolves around a shot from the GK.
There are a few reasons often cited to support this argument, one of which is that a large number of people seem to head up to the picket fence area in the immediate aftermath of the shooting which suggests a shot came from there.
In fact, this is not the case.
Apart from one man who races up the steps on seeing the head shot (I believe his wife and infant child are on a bench at the top of the steps) there is a gap of approximately 30 seconds before anyone thinks to run up the GK.
This excellent Cabluck/Cancellare composite from Robin Unger's gallery shows the exact moment (I've added the blue letters for enhancement). These four kids appear to be running after Haygood and end up following him to the top of the triple underpass.

The hordes of people approaching from the corner of Main and Houston, across the open grassy area of Dealey Plaza, see people running around the GK area and head for that. It is nothing to do with hearing shots from that area and witnesses like Marilyn Sitzman, stood feet away from this area, completely refute any notion of an audible shot from this area.