The latest US Presidential assassination attempts, starting with the most recent:

• (Actual attempt) - In April 2013, President Obama was mailed a letter which was deliberately laced with ricin. Ricin is an extremely deadly poison which is often used in bioterrorism. Luckily the poison was detected before the letter got to Obama.

  Mississippi Republican Senator Roger Wicker and Lee County Justice Court Judge Sadie Holland also received similar letters. The FBI arrested and imprisoned Everett Dutschke for sending the letters.

• (Actual attempt) - In November 2011, Oscar Ramiro Ortega-Hernandez, a delusional man who believed he was Jesus Christ and that Obama was the AntiChrist, approached the White House in Washington DC and opened fire on it with a semi-automatic rifle. There were no injuries but some damage to the building.
• (Foiled attempt) - In April 2009, a Syrian national was arrested when his plans to stab Obama during a press conference at a summit in Istanbul, Turkey, were foiled by security guards who noticed his journalist ID was a forgery.
• (Foiled attempt) - In October 2008, two white supremacists, Paul Schlesselman and Daniel Cowart, were arrested after their plans to assassinate Obama in a public drive-by shooting were discovered.
• (Actual attempt) - On the 10th May 2005, US President George W. Bush and Georgian President Mikheil Saakashvili survived an assassination attempt.

  While Bush was giving a speech in Freedom Square, the attempted assassin, Vladimir Arutyunian, threw a live hand grenade towards Bush and Saakashvili. The grenade didn't detonate because the handkerchief that it was tightly wrapped up in prevented the safety lever from detaching. The attempted assassin also killed a Interior Ministry agent in an attempt to resist capture.

You can find a full list of attempted US presidential assassinations on Wikipedia: https://en.wikipedia.org/wiki/List_of_United_States_presidential_assassination_attempts_and_plots

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