William O'Brien
William O'Brien (2 October 1852 – 25 February 1928) was an Irish nationalist, journalist, agrarian agitator, social revolutionary, politician, party leader, newspaper publisher, author and Member of Parliament (MP) in the House of Commons of the United Kingdom of Great Britain and Ireland. He was particularly associated with the campaigns for land reform in Ireland during the late 19th and early 20th centuries as well as his conciliatory approach to attaining Irish Home Rule.
William O'Brien (police officer)
William "Bill" O'Brien (March 10, 1944 – March 3, 2016) was an American police officer who served as the 21st Police Chief of Miami, Florida, from 1998 until 2000. O'Brien served as a Miami Police Department police officer for more than 25 years, including 18 years as a member of the city's SWAT team and two years as Miami Police Chief. He resigned as Police Chief on April 28, 2000, in the aftermath of the Elián González custody battle raid.