The correct answer to this open question is the following.
You vividly remember where you were when you heard about the Boston Marathon bombing. What you remember is a flashbulb memory and you are likely to be as accurate as a memory for an ordinary event.
Despite an event that happened when you were a child, you sometimes clearly remember it and with some details. That is a flashbulb memory. People commonly refer to it as a "vivid memory." The event had to be important or have a significant meaning for you. For instance, American citizens say they have a "vivid memory" of the moment President John F. Kennedy was assassinated.