Early on Wednesday morning (15 June), a congressman, aide and two police officers were shot as practice took place for the annual Congressional Baseball Game.
Nobody died in the incident, but GOP whip Steve Scalise was shot around five times in the hip and subsequently hospitalised.
The shooter, James T Hodgkinson, 66, died from wounds he sustained in a shootout with police. It was later revealed that he worked on a voluntary basis for the Bernie Sanders presidential campaign. The Independent senator said he was "sickened" by the events.
Despite the shooting, the game is set to go ahead today as planned.
The first game between Democrats and Republicans was held in 1909 after being organised by John Tener of Pennsylvania, a former professional baseball player.
What started out as a casual knockabout for politicians is now one of the most eagerly anticipated events on the Capitol.
It was initially held on a biennial basis with gaps during the Great Depression, the Second World War and a short spell in the late 1950's when House leadership thought it was too physically straining for congressmen to take part in.
In the early days, the two teams would normally wear plain coloured uniforms, but nowadays senators and representatives tend to wear the jerseys belonging to sports teams from their home states.
Both sides take the game seriously, but also use the occasion to raise money for various charities, with around $100,000 collected every year.
Despite the shooting the game will go on today (15 June) as planned.
Representative Barry Loudermilk (R-Ga.) said: "I think we need to go ahead and be on the field, and play this game for the kids."
Rep. Eric Swalwell (D-Calif.) said: "We'll go on, our resilience as a country, that's what makes us a strong country, but it'll be a different tone tomorrow."
This year the game will take place at Nationals Park in Washington DC, on the shores of the Anacostia River and just a 20-minute walk from Capitol Hill.
Republicans will be hoping to take a second successive victory in 2017, after seven-year dry spell.
Overall Dems have taken 39 wins, but the GOP have 42.