Washington (AFP) – The father of a teenager killed in a mass shooting at a Florida high school four years ago climbed a giant crane near the White House on Monday to urge President Joe Biden to take action against gun violence. Joaquin Oliver, 17, was one of 17 people who died when a former student opened fire with a semi-automatic weapon at Stoneman Douglas High School in Parkland, Florida, on February 14, 2018. His father, Manuel, scaled a giant crane at a construction site near the White House in downtown Washington early on Monday and unveiled a banner with a picture of his slain son. “45K…