Fyodor Nikolayevich Kozlov (Russian: Федор Николаевич Козлов; 9 April 1959 – 1 September 1990), known as The Iskitim Maniac (Russian: Искитимский маньяк), was a Soviet serial killer and rapist who committed a series of murders in three oblasts from 1976 to 1989. Convicted and sentenced to death for these crimes, he hanged himself in prison before the verdict could be carried out.

Eric David Harris (April 9, 1981 – April 20, 1999) and Dylan Bennet Klebold ( KLEE-bohld; September 11, 1981 – April 20, 1999) were American high school seniors and a mass murderer duo who perpetrated the massacre at Columbine High School on April 20, 1999, in Columbine, Colorado. Harris and Klebold killed 13 students and one teacher and wounded 23 others.

Martha Needle (née Charles; 9 April 1863 – 22 October 1894) was an Australian serial killer who was hanged for poisoning her husband, three children, and prospective brother-in-law. She was convicted for the murder of Louis Juncken, brother of her fiancé Otto Juncken, on 15 May 1894.

Stephen Craig Paddock (April 9, 1953 – October 1, 2017) was an American mass murderer who perpetrated the 2017 Las Vegas shooting. Paddock opened fire into a crowd of about 22,000 concertgoers attending a country music festival on the Las Vegas Strip, killing 60 people and injuring approximately 867 (at least 413 of whom were wounded by gunfire).

John Overton (April 9, 1766 – April 12, 1833) was an American planter and slave trader, a judge at the Tennessee Supreme Court, a banker, political leader, and an advisor of Andrew Jackson. He was described in 1889 as having been the "wealthiest man in the State."

Leopold II (9 April 1835 – 17 December 1909) was the second king of the Belgians from 1865 to 1909, and the founder and sole owner of the Congo Free State from 1885 to 1908.