One congressman and five others were injured Wednesday morning when a gunman open fired at a Virginia baseball field where Republican congressmen were practicing for Thursday's annual Republican versus Democrat charity Congressional Baseball Game.

Victims

Rep. Steve Scalise (R-LA) is in critical condition, according to CNN, and it is unclear if he will need a second surgery.

His wife and two children are en route from Louisiana to be with him at MedStar Washington Hospital Center in Washington, D.C. He was shot several times in the hip. Scalise is the Majority Whip, the third-ranking House Republican.

Legislative aide Zachary Barth is "okay" according to a Facebook post, NBC reported. Barth is a legislative correspondent for Rep. Roger Williams (R-TX).

Williams sprained his ankle while seeking cover. At a press conference Wednesday afternoon, Williams said he will still be at Thursday's game.

Matt Mika, a lobbyist for Tyson Foods, regularly attends practice to help coach the team.

He was shot in the chest, and bullets missed his heart. Mika is in critical condition.

Two members of US Capitol Police were injured. Crystal Griner is in good condition after being shot in the ankle, according to CNN. David Bailey has been released from the hospital after sustaining a minor injury while returning fire.

US Capitol Police were on scene as part of Scalise's security detail.

Lawmakers React

Lawmakers credit US Capitol Police for their response.

"It would have been a massacre without them," Sen. Rand Paul (R-KY) told CNN.

Rep. Joe Barton (R-TX) and Rep. Michael Doyle (D-PA), the head coaches for the Republican and Democratic baseball teams, held a joint press conference Wednesday afternoon.

Barton was at practice with his two sons. His youngest son, 10 year old Jack, was on the opposite side of the baseball fence when the shooting started, Barton said. He instructed his son to hide underneath a car while he hid in a dugout with his fellow players.

"He had 25 dads," Barton said. "Everyone out there was looking out for him, not just me."

FBI Press Conference

"This is an active investigation and details continue to unfold," FBI Special Agent Tim Slater said at a press conference Wednesday afternoon.

Slater clarified that four people were shot, and that two others - a congressman and a US Capitol Police officer, sustained secondary injuries at the scene.

The FBI believes the shooter has been in the Alexandria area since March, Slater said.

The shooter is a resident of Illinois, and the FBI believes he has been living out of his vehicle.

Slater identified the weapons used by the shooter as one hand gun and one rifle.

The FBI hopes the investigation will provide the motive of the shooter and how the weapons were obtained.

Anyone with information on the shooter is encouraged to contact the FBI.