The shooter, who had a violent history including arrests for battery, resisting arrest and drunken driving, was identified as 66-year-old James T. Hodgkinson, of Illinois, Fox News confirmed. President Trump said Hodgkinson died from injuries sustained when he was shot by police.
"I have just been informed that the alleged shooter at the Republican baseball practice is someone who apparently volunteered on my presidential campaign," Sanders said in a statement. "I am sickened by this despicable act. Let me be as clear as I can be. Violence of any kind is unacceptable in our society and I condemn this action in the strongest possible terms."
President Trump addressed the nation before noon and revealed Hodgkinson died in police custody.
"Steve Scalise was shot and badly wounded and is now in stable condition at the hospital along with two very brave Capitol Police officers," Trump said in a White House address. "At least two others were also wounded."
Zack Barth, a congressional aide to Rep. Roger Williams, R-Texas, and Tyson Foods director of government relations Matt Mika were also injured in the incident. Mika was shot multiple times and was in critical condition, his family said in a statement.
Special Agents David Bailey and Crystal Griner were both wounded in the incident. Griner was shot in the foot or leg and Bailey, who was not shot, sustained another, unspecified injury.
“Congressman Scalise is a friend and a very good friend,” Trump said. “He’s a patriot and a fighter. He will recover from this assault. And, Steve, I want you to know that you have the prayers of not only an entire city behind you, but the entire nation – and frankly the entire world.”
Rep. Ron DeSantis, R-Fla., told Fox News he left just before the shooting. As he walked to his car, a man asked DeSantis if it was Republicans or Democrats practicing. About 3 minutes later, at around 7:09 a.m., the shooting began, DeSantis said. He later told Fox Business he believed the man who approached him was the shooter.
Sen. Rand Paul, R-Ky., described the chaotic scene to Fox News: "We were like sitting ducks."
"Without the Capitol Hill police it would have been a massacre," Paul said, calling the scene "sort of a killing field."
Hodgkinson was shot by Capitol Police and Alexandria Police, apprehended and taken to the hospital, officials said. The incident occurred at Simpson Field in Alexandria, about 10 miles from Washington D.C. The FBI was taking over the investigation because a federal official -- Scalise -- was assaulted in the attack.
"An attack on one of us is an attack on all of us," House Speaker Paul Ryan said in an address from the floor of the House of Representatives. His words were greeted by a bipartisan standing ovation from the gathered legislators.
Ryan added: "We are all one family. These are our brothers and sisters who were in the line of fire."
FBI Special Agent in Charge of the Washington Field Office Timothy Slater said it was too early to tell if the attack was terror-related.
Trump had spoken to Senate Majority Leader Mitch McConnell, Ryan, Scalise's wife and chief of staff and the chief of the Capitol Hill Police.
The Department of Homeland Security was monitoring the episode.
Williams was seen being taken from the field on a stretcher, but he was reportedly injured while jumping into the dugout as the shots rang out.
"Finally, the shooter was shot behind home plate as he was circling around to the first base dugout where there were a number of US congressmen and other folks," Rep. Mo Brooks, R-Ala., told FMTALK1065. "Our security detail was able to incapacitate him at that point. I don't know if he [the shooter] was dead. He was wounded. I don't know how many times he was wounded."
Brooks reportedly used a belt as a tourniquet to stop the bleeding of an aide who was shot in the leg.
Rep. Brad Wenstrup, R-Ohio, told Fox News he "felt like I was in Iraq, but without my weapon."
"Behind third base, I see a rifle...I hear Steve Scalise over near 2nd base scream," Brooks said. "...While all of this is going on, Steve Scalise our whip was lying on the ground near the second base position crawling into right field, leaving a trail of blood."
Brooks said the gunman was using the dugout as cover and estimated the assailant got off 50-100 shots during the attack on the 15-25 people gathered at the field.
“We were there within 3 minutes,” Brown said. “Two of our officers engaged in gunfire and returned fire.”
A man walking his dog at a park near the field told Fox News he heard police yelling at the gunman to put the gun down followed by someone in or around the dugout screaming back "Just shoot him."
Aside from Scalise, Williams, Paul, Brooks, Wenstrup and DeSantis, Sen. Jeff Flake and Reps. Mike Bishop, Jack Bergman, Chuck Fleischmann and Joe Barton were also at the field. A photographer and Bishop's aides were present, too.
Alexandria schools were placed on lockdown as the incident unfolded. There was an uptick in the police presence around the Capitol, however, the building was still open. There was not expected to be any votes held on Wednesday in light of the shooting.
Witnesses and residents described a shattered calm Wednesday morning in a normally peaceful neighborhood now plastered with police tape.
Reba Winstead, who lives in the area, described hearing a “boom boom boom boom." She said she was getting her daughter ready for school and then “all of a sudden there was gunfire in our neighborhood.”
Scalise, 51, is the House majority whip. He has represented Louisiana’s 1st Congressional District since 2008 and chairs the House Republican Study Committee. He is married with two children. Scalise's district includes New Orleans.
Since he's in leadership, Scalise has a security detail.
Scalise, who studied computer science at Louisiana State University, worked as a systems engineer before launching his political career. Scalise endorsed President Trump during last year’s presidential campaign, and has been a vocal backer of Trump’s travel ban. As leader of the powerful study group, he has also spearheaded the effort to repeal and replace ObamaCare.
The Congressional Baseball Game is scheduled for June 15 at Nationals Park. The game, which has been a tradition since 1909, pits Senate and House members of each party who sport the uniform of their home state.
Congressional leaders said the game would go on as planned.