Brutus had always been a loyal supporter of Julius Caesar and was considered his close friend. However, Cassius was able to convince Brutus that Caesar wished to rule Rome as a monarch. Being an honorable man, Brutus makes the difficult decision to join the conspirators. Julius Caesar is completely caught off guard on the Senate floor and does not expect Brutus to betray him, which is why some of his last words are "Et tu, Bruté?" "And you, Brutus?" Julius Caesar trusted that Brutus was a loyal friend, similar to Mark Antony, and was astonished to discover that Brutus betrayed him.
We hold these truths to be self-evident, that all men are created equal, that they are endowed by their Creator with certain unalienable Rights, that among these are Life, Liberty and the pursuit of Happiness.
Jefferson says here that the creator of mankind has endowed or given these rights to humanity.
Explanation: By saying that the dust was once a man, he is saying no one remembers Lincoln, what used to be a great and powerful man, is now dust, forgotten and insignificant.