From the sounds of it, your essay is going to resemble a piece of historical fiction. Your setting, events, and possible surrounding people are real, but your character isn't necessarily real. That helps a lot, because it lets you create who you want your character to be. That should be your first step. Who do you want to be? A visiting tourist? A Haiti native? A first responder?
I recommend being a visiting tourist or a first responder. The visiting tourist won't be that far of a stretch for you. I'm assuming that you are not a resident of Haiti, so writing about Haiti with a general sense of awe and limited knowledge is exactly where you are personally at anyway. The first responder is a good choice too, because it lets you write about the earthquake damage and sequence of events from the perspective of somebody that knows about them. It would sound weird for a visiting tourist to know a lot of details about the extent of the damage on that day, but a first responder would be getting information via radio communications from all over. That can work to your advantage as the essay writer, because the prompt asks you to write about actual historical events. You are going to need some facts.
Research facts about the Haiti earthquake. You are going to find a ton, so be picky. Focus on events that make sense based on who your character is and what your general plot line is. For example, what the response from the United States might be (was) wouldn't likely concern a native from Haiti. But it would be at the forefront of the mind of a U.S. citizen visiting there.