(CNN) For most people, their first thought upon hearing of the shootings at a baseball practice for Congressional Republicans went something like this: Why are members of Congress on a baseball diamond at 7 a.m. on a weekday?

The answer is the Congressional Baseball Game, a tradition among lawmakers going back to the early part of the 20th Century that in recent years has raised $600,000 for charity.

"It's one of the best things we do," Sen. Rand Paul, who was at the practice when the shooting broke out, told CNN Wednesday morning.

"Every year, with a few interruptions, Senate and House members of each party team up to settle scores and solidify friendships off the floor and on the field," according to the game's website . "Members usually sport the uniform of their home states and districts, and although proportional representation is not required, elected officials of many states play to win every year."

In the run-up to the game, which is scheduled to be played tomorrow at Nationals Park, both sides -- Republicans and Democrats -- hold early-morning practices in neighborhoods around Washington.