Edward V was a minor, so his uncle Richard, Duke of Gloucester, was made Protector by the will of Edward IV. Richard had been loyal throughout to his brother Edward IV including the events of 1470-71, Edward's exile and their brother's rebellion (the Duke of Clarence, who was executed in 1478 by drowning, reputedly in a barrel of Malmsey wine). However, he was suspicious of the Woodville faction, possibly believing they were the cause of Clarence's death.
In response to an attempt by Elizabeth Woodville to take power, Richard and Edward V entered London in May, with Edward's coronation fixed for 22 June. However, in mid-June Richard assumed the throne as Richard III (reigned 1483-85).
Edward V and his younger brother Richard were declared illegitimate on the grounds that Edward IV had a marriage contract with Lady Eleanor Butler before his marriage to Elizabeth Woodville. They were taken to the Royal apartments at the Tower of London (then a Royal residence) and never seen again. (Skeletons, allegedly theirs, found there in 1674 were later buried in Westminster Abbey.)
There is some debate about whether Richard III or Henry VII was ultimately responsible for the boys' deaths.