Answer:
The event happened due to two men having hatred for America and feeling as if they should cause harm to others based on the opinion they have, when the massacre happened the two brothers placed bookbags with makeshift bombs that were timed to explode in the middle of the crowd watching the race two brothers then walked away ad the bombs went off causing major injury and death to the people in the radius of the bookbag, when everyone realized what was happening panic ensued and everyone started running as the police ran to save people.
Explanation:
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