On this day in 1999, two teenage gunmen kill 13 people in a shooting spree at Columbine High School in Littleton, Colorado, south of Denver.

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Many historical events occurred on April 4th, and Russ Mitchell recaps them in this video clip from This Day In History. President William Henry Harrison became the first US President to die while in office when his cold turned into pneumonia. Congress passed and authorized what would become known as the American flag, with 13 strips, and then 20 stars with a blue background. Each state that would be added would add another star to the flag. Also, the first Mexican American, Henry Cisneros, became mayor of a major city, which was Texas. On Martin Luther King Jr.'s Memphis hotel balcony, James Earl Ray assassinated King.

On this day in 1929 in Chicago, gunmen in the suspected employment of organized-crime boss Al Capone murder seven members of the George "Bugs" Moran North Siders gang in a garage on North Clark Street. The so-called St. Valentine's Day Massacre stirred a media storm centered on Capone and his illegal Prohibition-era activities and motivated federal authorities to redouble their efforts to find evidence incriminating enough to take him off the streets. Alphonse Capone was born in Brooklyn in 1899, the son of Italian immigrants from Naples. In 1921 his old friend Johnny Torrio lured him to Chicago, where Torrio had built up an impressive crime syndicate and was beginning to make a fortune on the illicit commerce of alcohol. In 1925, Torrio was shot four times by Bugs Moran and Hymie Weiss, who were associates of a gangster slain by Torrio's men. Capone was in Florida in February 1929 when he gave the go-ahead for the assassination of Bugs Moran. On February 13, a bootlegger called Moran and offered to sell him a truckload of high quality whiskey at a low price. Moran took the bait and the next morning pulled up to the delivery location where he was to meet several associates and purchase the whisky. He was running a little late, and just as he was pulling up to the garage he saw what looked like two policemen and two detectives get out of an unmarked car and head to the door. Thinking he had nearly avoided being caught in a police raid, Moran drove off. The four men, however, were Capone's assassins. Wearing their stolen police uniforms and heavily armed, Capone's henchmen surprised Moran's men, who agreed to line up against the wall. Thinking they had fallen prey to a routine police raid, they allowed themselves to be disarmed. A moment later, they were gunned down in a hail of shotgun and submachine-gun fire. Six were killed instantly, and the seventh survived for less than an hour.

The great San Francisco earthquake killed 3,000 people, Paul Revere's midnight ride took place, physicist, Albert Einstein died, and play ball began a Yankees and Red Sox game for the first time in This Day in History video. The date is April 18th. Paul Revere's ride resulted in the battles of Lexington and Concord and signaled the beginning of the Revolutionary War.

After Napoleon Bonaparte failed to unite all of Europe under his rule, he was thrown off his throne by the neighboring nations during the War of Liberation on April 11th. This event along with others on April 11, is recapped in this video clip. The video clip, narrated by Russ Mitchell from This Day In History also includes the crowning of William III and Mary II as King and Queen of England, and the launch of Apollo 13. Also on April 11, Chinese officials agreed to release the crew of the plane that was involved in the US-China Spy Plane Incident, which killed a Chinese pilot.

Jesse James, one of the most wanted bank and train robbers was shot in the back by one of his gang members for the reward on April 3rd. Russ Mitchell recaps this and other events that occurred on April 3rd in this video clip from This Day In History. The day before Martin Luther King Jr. was assassinated, April 3, he gave his famous mountain speech. A resolution to end the Gulf War was passed by the UN Security Council, and the fasted mail service at the time in the west, The Pony Express, began on this day.

LSD the hallucinogenic is discovered, Lenin returns to Russia during the Russian Revolution, Mick Jagger and the Rolling Stones release their first album, and Wayne Gretzky retires from hockey in This Day in History video. The date is April 16th. Vladimir Lenin, a Russian revolutionary, is famous for initiating what many call the October Revolution.