Short answers, pulled from the story.
Mehmet Ali Ağca, a Turkish national, shot Pope John Paul II on the 13th of May 1981 in St. Peter's Square, Vatican City. Ağca fired four shots with a 9mm Browning Hi-Power semi-automatic pistol at 17:17, striking the Pope twice.
The assassination attempt took place in St. Peter's Square in Vatican City on the 13th of May 1981. Ağca opened fire at 17:17 as the Pope's motorcade passed through a crowd of supporters.
Yes. Pope John Paul II publicly asked people to pray for Ağca as "my brother... whom I have sincerely forgiven." In 1983 the Pope visited Ağca at Rome's Rebibbia Prison, and he later secured Ağca's pardon from Italian president Carlo Azeglio Ciampi in June 2000.
No conclusive proof was ever established. The theory that the KGB ordered the attack because of the Pope's support for Poland's Solidarity movement was widely promoted in the 1980s, but former CIA analyst Melvin A. Goodman told the US Senate intelligence committee in 1991 that colleagues had falsified their analysis and that "the CIA hadn't any proof." The main accused, Sergei Antonov, was found not guilty after a three-year trial ending in 1986.
Ağca spent nearly 29 years behind bars in total. An Italian court sentenced him to life imprisonment in July 1981, but he was pardoned in June 2000 and deported to Turkey, where he served additional time for the 1979 murder of journalist Abdi İpekçi and other offenses. He was finally released on the 18th of January 2010.
The shooting on the 13th of May 1981 fell on the 64th anniversary of the first reported apparition of the Virgin Mary at Fatima on the 13th of May 1917. On the 13th of May 2000, Cardinal Angelo Sodano publicly linked the Third Secret of Fatima to the attack, and the full text of the Third Secret was released by the Vatican on the 26th of June 2000.