Short answers, pulled from the story.
Duke Charles III of Bourbon led the Imperial army toward Rome on the 20th of April 1527. He commanded a force that included 14,000 Germans known as Landsknechte under Georg von Frundsberg and 6,000 Spaniards.
The Imperial army attacked the Aurelian Walls at the Gianicolo and Vatican hills on the 6th of May 1527. Duke of Bourbon died fatally wounded while wearing his famous white cloak during this assault.
An estimated 6,000 to 12,000 people died during the sack itself. The city's population dropped from over 55,000 before the attack to just 10,000 afterward due to atrocities famine plague and flight.
Imperial forces imprisoned Pope Clement VII following the sack of Rome. Emperor Charles V eventually restored spoils worth more than 4 million ducati to the Vatican through the Treaty of Barcelona signed in 1529.
Funds were simply not available to pay the 34,000 men in the Imperial Army which made them desperate and mutinous against their commanders. Without wages these soldiers became desperate and began pillaging churches monasteries and palaces immediately after executing about 1,000 defenders.