Notice the proximity of the march to the pro-Chávez crowd. This is the most well-documented killing; captured by several photographers and two camera crews (likely for the very reason that it was the first killing; none of the journalists were worried about being shot...yet).
Of course, the fact that the first fatality was caused by the pro-Chávez gunmen has tremendous implications for the ensuing coup. Now the government's narrative about a premeditated plan on the part of the opposition collapses. That is, the government cannot charge the opposition with placing gunmen at the head of the march to cause deaths to spark a coup.