Death in SAO before Kayaba announcement
So, I read the beginning of the novel, and like Ayase Eri said, Kayaba is fair so he hadn't killed the players before doing an announcement.

This is written on page 71 :


  The first person to get the honor of having his name crossed out
  appeared three hours into the game. The reason for death was not losing to a monster. It was suicide.
  
  He believed in the theory that "according to the structure of the NerveGear, if a person is cut off from the system they'll automatically regain consciousness." He climbed over the iron fence at the north end of the city, or the edge of Aincrad, and flung himself off.


So, it clearly means that it was after Kayaba did his announcement because he tried to escape the game.

The anime followed that as well and if I remember it right, we see that first death (but I do not remember if it was during the first episode or a flashback that we see it).

The author really kept the characteristics of every character to this point.