Answer:
The tragedy in Romeo and Juliet.
Step-by-step explanation:
When Romeo says these words "The future will be affected by today's terrible events." He is talking about the fight with Tybalt. (Spoiler alert!) He is saying that how something bad will happen in the future after murdering Tybalt. He also says "Today is the start of a terror that will end in the days ahead." Tybalt has died, and Romeo says that he may end up in the same place as Tybalt (Another spoiler alert!). So, "Today is the start of a terror" is about the fight, and "will end in the days ahead" means that Romeo will die too, mainly because of the feud he had with the Capulet. Hope this helps!