The 1954 United States Capitol shooting was an attack on March 1, 1954, by four Puerto Rican nationalists wanting Puerto Rico's independence from US rule. They shot 30 rounds from semi-automatic pistols from the Ladies' Gallery (a balcony for visitors) of the House of Representatives chamber in the United States Capitol.

Five Representatives were wounded, one seriously, but all recovered. The assailants were arrested, tried and convicted in federal court, and given long sentences, effectively life imprisonment. In 1978 and 1979, their sentences were commuted by President Jimmy Carter. All four returned to Puerto Rico.

https://en.wikipedia.org/wiki/1954_United_States_Capitol_shooting