What Was The Role of David Herold

[John E.]

I believe that Herold's responsibility that evening was to be the point / signal man of all three attacks.

If all the attacks were to be coordinated, someone had to relay to the others that things were still a "go". So, Herold seeing that Booth was going through with the assassination, rode somewhere near Seward's home to signal to Powell that things were moving forward. Powell received the signal and proceeded.

Herold then went to signal Atzerodt to do the same. He very well could have been the person that went to the room at the Kirkwood and tried to open the door. Atzerodt said he didn't relinquish the keys to Herold. Makes sense.

Like Wesley said, this is all speculation without proof. Still fun to guess.