Updated 5:46 p.m. Eastern Standard Time
Rep. Brad Wenstrup, a podiatrist and colonel in the Army Reserve who deployed to Iraq from June 2005 to May 2006, was the first to aid Rep. Steve Scalise, the House majority whip and third-ranking Republican in the House who was shot in the incident in Alexandria, Virginia, according to a source familiar with the incident.
"I felt like I was back in Iraq," Wenstrup said afterward during an interview with CBS News.
The congressman was with his family later Wednesday morning and not immediately available for an interview but his office did provide the following statement:
"You never expect a baseball field in America to feel like being back in a combat zone in Iraq, but this morning it did," Wenstrup said. "Capitol police and emergency responders reacted swiftly and courageously -- we are grateful for their presence. I urge the nation to keep Rep. Scalise and all injured in their prayers today."
There were five shooting victims. In addition to Scalise, the others were identified as Zachary Barth, a congressional aide; Matt Mika, a lobbyist; and Special Agents David Bailey and Krystal Griner, both Capitol Police officers, according to information released by House speaker's office.
They were initially believed to be in non-life-threatening condition. Scalise and Mika were later listed in critical condition, CNN reported. Bailey was treated and released for a minor injury, and Griner is in good condition after being treated for a gunshot wound to the ankle, according to a statement from the U.S. Capitol Police.
The incident took place at a practice in advance of the annual, long-running baseball game between members of both political parties in Congress.
Authorities didn't say whether the incident was an assassination attempt.
Wenstrup said Scalise "was conscious" and "very brave" while receiving medical care at the scene and praised the efforts of Capitol Hill police who returned fire at the gunman, James Hodgkinson, 66, of Illinois.
The shooter, who later died, had volunteered on the presidential campaign of Sen. Bernie Sanders, an Independent from Vermont who ran in the Democratic presidential primary against Hillary Clinton. In a speech, Sanders deplored the gunman's actions.
Hodgkinson was described as wielding a 30-caliber rifle, though police didn't identify the make or model of the weapon.
Scalise is "under care right now -- I assume he's in surgery right now," Wenstrup told NBC News. "But he was aware of where he was and what was going on."
Wenstrup, a Medical Service Corps officer who received the Bronze Star Medal, Combat Action Badge and other awards, according to his service records, described his actions at the scene.
"I saw that he was down, and then I went out to him after they had subdued the shooter," he said.
When asked to describe what the mood at the field was like, Wenstrup told the network, "We were upbeat, getting ready for a game. And something like this happens, and you can't believe it."
He said, "Fortunately, there's the security detail there -- the Capitol Hill police -- or we all would have been vulnerable without return fire. So I'm sure they saved who knows how many lives."
Wenstrup added, "Let's pray for those that did get hit today."