House Majority Whip Steve Scalise (R-LA) speaks to reporters at the US Capitol, hours before an expected vote to repeal Obamacare in Washington, D.C., US on May 4, 2017.? [Photo/Agencies]

ALEXANDRIA, Va. - A man who had posted angry messages against President Donald Trump and other Republicans on social media opened fire on Republican lawmakers practicing for a charity baseball game on Wednesday, wounding a senior US House member and three other people.

The gunman, a 66-year-old Illinois man, fired repeatedly at the men playing on a baseball field in suburban Alexandria, Virginia, near Washington, D.C.

He was wounded in a gunfight with Capitol Hill police who were at the scene, and police said he later died.

Steve Scalise, the No. 3 Republican in the House of Representatives, was shot in the hip. He was tended to by fellow lawmakers including Brad Wenstrup, a congressman who is a physician, before being transported to a hospital, where he was listed in critical condition.

Also wounded were one current congressional aide and one former aide who now works as a lobbyist, officials said. One Capitol Hill police officer suffered a gunshot wound and another officer twisted an ankle, an official said.

While police and the Federal Bureau of Investigation said it was too early to determine whether it was a deliberate political attack, the shooting intensified concerns about the sharp divide and bitter rhetoric in US politics.

It also quickly revived debate about gun rights in America. Virginia's Democratic governor, Terry McAuliffe, urged gun control measures. "This is not what today is about, but there are too many guns on the street," McAuliffe said at a news conference near the scene of the shooting.

Scalise has been a strong opponent of gun control measures.

The gunman was identified by a senior US official as James Hodgkinson from the St. Louis suburb of Belleville, Illinois. He had worked as a home inspector.

Hodgkinson had raged against Trump on social media and was a member of anti-Republican groups on Facebook including, "The Road to Hell Is Paved With Republicans," "Terminate The Republican Party," and "Donald Trump is not my President," a search of his Facebook profile showed.

As businessman Trump rose to become the Republican Party nominee in the 2016 presidential election, his brash style and outspoken views on immigration and other policies led to mass protests, including on the weekend of his inauguration in January.

Representative Tim Ryan, who early on Wednesday was practicing for the ballgame with fellow Democrats, told reporters that Washington politicians needed to cool their rhetoric.

"We've got to get back to...where things aren't so personal and we're so judgmental of each other. It's got to stop. A member of the US Congress got shot because they didn't like (his) political views," Ryan said.

CALLS FOR UNITY

Trump announced the gunman's death and called Scalise, a 51-year-old Louisiana congressman, a good friend. "He's a patriot and he's a fighter. He will recover from this assault," Trump said.

Trump also called for unity. "We are strongest when we are unified and when we work together for the common good," he said.

In a show of bipartisanship, Republican House Speaker Paul Ryan said on the floor of the House, "An attack on one of us is an attack on all of us." The House's top Democrat Nancy Pelosi echoed Ryan's message.

The shooting happened shortly after 7 a.m., while lawmakers were practicing their hitting and fielding a day before the annual charity congressional baseball game pitting Republicans against Democrats.

There were 20 House members and two senators present, and the shooting lasted about 10 minutes, said Representative Joe Barton, the Republican team's manager.

The charity game will go ahead as scheduled at Nationals Park, home of the Washington Nationals Major League Baseball team.

Two lawmakers who were at the scene, Representatives Ron DeSantis and Jeff Duncan, indicated there might have been a political motive in the attack.

Duncan said that as he left the field the man who would later open fire approached him in the parking lot. "He asked me who was practicing this morning, Republicans or Democrats, and I said, 'That's the Republicans practicing'," Duncan told reporters. DeSantis gave a similar account.

Senator Bernie Sanders, an independent who sought the 2016 Democratic presidential nomination, said he had been told that Hodgkinson had served as a volunteer with his campaign.

"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," Sanders said.

Ryan, the House speaker, is reviewing rules on how rank-and-file lawmakers can increase their personal security, including questions about paying for additional protection through member accounts and campaign funds, according to several lawmakers.

"Members get threats on a regular basis and have trouble determining which are real," House Democratic whip Steny Hoyer told reporters.

Representative James Clyburn, a Democrat, rejected the idea that the shooting was motivated by partisan politics. "I'm not a Republican and I've had all kinds of threats against me and my family. It's got nothing to do with partisan politics."

'HEROISM' OF POLICE

The shooting took place at Eugene Simpson Stadium Park in the Del Ray neighborhood of Alexandria, across the Potomac River from Washington.

Representative Mo Brooks told CNN that during batting practice he heard a "bam" and then a quick succession of shots and saw the gunman shooting through the holes in a chain link fence.

When Scalise was shot he went down on the infield between first and second base, then dragged himself into the grassy outfield as the incident unfolded, leaving a trail of blood, Brooks said.

Two Capitol police officers who were there to provide security for the lawmakers engaged the gunman with pistols, Brooks said.

"But for the Capitol police and the heroism they showed, it could very well have been a large-scale massacre. All we would have had would have been baseball bats versus a rifle. Those aren't good odds," Brooks said.

Brooks estimated 50 to 100 shots were fired.

Wednesday's attack was the first shooting of a member of Congress since January 2011, when Democratic Representative Gabby Giffords was seriously wounded in an assassination attempt at a gathering of constituents in Tucson, Arizona. She survived, but six people were killed. Giffords resigned from Congress and became an activist for gun restrictions.