Video has emerged of the chaos that broke out the moment 66-year-old James Hodgkinson opened fire on a GOP practice session for a charity baseball game between congressional Democrats and Republicans.
Scalise's office said earlier Wednesday that he was in stable condition following the shooting, although MedStar Washington Hospital Center said Wednesday afternoon that Scalise remained in critical condition.
Authorities did not immediately reveal why Hodgkinson opened fire. The gunman, identified as James T. Hodgkinson, campaigned for Sanders in Iowa, ahead of the first-in-the-nation caucuses in February 2016.
In all, according to local police, five people were taken to the hospital after the shooting, including Hodgkinson. They included the gunman, according to the Washington Post.
The event raised questions about the security of members of Congress.
Two police officers, a congressional aide and a lobbyist were also shot.
After the election, Hodgkinson often posted angry rhetoric online directed at Donald Trump.
Federal Bureau of Investigation special agent in charge Tim Slater said it was "too early to say" whether it was an act of terrorism, or whether Scalise was targeted. "They speak their lies and hatred and misdirection to anyone who will listen".
When informed that Hodgkinson had worked for his campaign, Sanders issued a statement condemning the attack.
"When tragedy strikes we are family", said Rep. Nanette Barragan of California, who plays on the Democratic baseball team and invited all to attend the charity baseball game Thursday night at Nationals Stadium.
"All of a sudden, we heard a loud, what sounded like a gunshot, very loud and very close", Sen.
"The only thing I was concerned about was that it was such a high-powered gun, and that somebody could possibly get hurt".
"I told the sheriff, 'I don't know what's the matter with that guy, but he can't be shooting like that, '" he said.
Senator Rand Paul, also at the practice, said he believed the rapid intervention narrowly prevented a bloodbath. "America is praying for you and America is praying for all of the victims of this bad shooting".
Davis, who was at bat at the time of the shooting, said he hopes Wednesday marks a turning point in how lawmakers engage in the future. He said Hodgkinson spent most of his life building homes but in recent years turned to home inspections. Now we know where he went. He said Hodgkinson was not a staffer and had no formal role in the campaign. "The whip was in good spirits and spoke to his wife by phone", the statement read. He served as a member of Louisiana's state Legislature for 12 years before being elected to the U.S. House.
That noted political philosopher, Madonna, thinks a lot about blowing up the White House.
Lawmaker Brooks described Scalise dragging his body across the pitch to get away from the shooter while the firing continued.
He shot the third-highest-ranking House Republican, whip Steve Scalise, and injured four others at the field just outside of Washington about 7am on Wednesday (9pm AEST).