Cooley implants the first temporary artificial heart. April 8 – The Montreal Expos become Major League Baseball's first team outside the United States. April 9 – Fermín Monasterio Pérez is murdered by the ETA in Biscay, Spain; the 4th victim in the name of Basque nationalism. April 13 – Queensland: The Brisbane Tramways end service after 84 years of operation. April 15 – The EC-121 shootdown incident: North Korea shoots down the aircraft over the Sea of Japan, killing all 31 on board. April 17 – Sirhan Bishara Sirhan is found guilty of the assassination of Robert F. Kennedy. April 20 – British troops arrive in Northern Ireland to reinforce the Royal Ulster Constabulary. April 22 – Robin Knox-Johnston becomes the first person to sail around the world solo without stopping. April 28 – Charles de Gaulle steps down as president of France after suffering defeat in a referendum the day before. May May 4 Zakir Husain, President of India, dies due to a heart attack. In a repeat of the previous season's hockey finals, the Montreal Canadiens defeat the St. Louis Blues four games to none to win the Stanley Cup. May 10 – The Battle of Dong Ap Bia, also known as Hamburger Hill, begins during the Vietnam War. May 13 – May 13 Incident: Race riots occur in Kuala Lumpur, Malaysia. May 14 – Colonel Muammar Gaddafi visits Mecca, Saudi Arabia. May 15 – An American teenager known as 'Robert R.' dies in St. Louis, Missouri, of a baffling medical condition. In 1984 it will be identified as the earliest confirmed case of HIV/AIDS in North America. May 16 – Venera program: Soviet space probe Venera 5 lands on Venus. May 17 – Venera program: Soviet space probe Venera 6 begins to descend into Venus's atmosphere, sending back atmospheric data before being crushed by pressure. May 18 – Apollo program: Apollo 10 (Gene Cernan, Tom Stafford, John Young) is launched. It is to be a full rehearsal for the Moon landing, stopping 15 kilometers short of actually reaching the lunar surface. May 20 – United States National Guard helicopters spray skin-stinging powder on anti-war protesters in California. May 21 – Rosariazo: Civil unrest breaks out in Rosario, Argentina, following the death of a 15-year-old student. May 22 – Apollo program: Apollo 10's lunar module flies to within 15,400 m of the Moon's surface. May 26 The Andean