Update 6:23pm: Democratic Senator Bernie Sanders has said the gunman who shot Republican politician Steve Scalise had apparently volunteered on his presidential campaign.
Mr Sanders said in a statement, "I am sickened by this despicable act."
He said that "violence of any kind is unacceptable in our society and I condemn this action in the strongest possible terms".
He paid tribute to Capitol Police for their response to the shooting, and said his "hopes and prayers" are with Mr Scalise and others who were wounded.
Mr Sanders challenged Hillary Clinton for the Democratic nomination in the 2016 presidential election.
He added in his statement that "real change" can only come through non-violent action.
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. pic.twitter.com/ib2reH3ghQ— Bernie Sanders (@SenSanders) June 14, 2017
Earlier: The gunman who shot a Republican politician Steve Scalise and several others as they practised baseball had had a number of run-ins with police in recent years.
These included arrests for battery, resisting arrest and drink-driving.
James T Hodgkinson, who was 66 and from Illinois, was shot by police.
Court records show that his legal trouble started in the 1990s.
His most serious problems apparently came in 2006, when he was arrested on the battery charge.
Records indicate he has not been involved in any legal cases since 2011.
Earlier:The gunman who shot a Republican politician Steve Scalise at a congressional baseball practice has died from his injuries, US President Donald Trump said.
Mr Trump said the assailant who shot Representative Steve Scalise, of Louisiana, had died.
He has been identified as James T Hodgkinson.
Mr Scalise was shot at a congressional baseball practice just outside of Washington.
Officials said several other people were also wounded.
Mr Trump said Mr Scalise "was badly wounded and is now in stable condition".
The president praised the "heroic actions" of the Capitol Police at the scene.
Earlier: Capitol Police said officers who were part of Mr Scalise's security detail returned fire and wounded the shooter, who was taken into custody.
Mr Scalise was shot by a rifle-wielding gunman at a congressional baseball practice just outside of Washington.
In all, five people were taken to hospital, including the suspect, Alexandria police said.
A law enforcement official said the shooting is being investigated as a criminal act rather than an act of terrorism.
Mr Scalise, 51, the number three House Republican leader first elected to the House in 2008, is in a stable condition and undergoing surgery at a nearby hospital.
His injuries are not believed to be life-threatening.
The shooting occurred at a popular park and baseball complex in Alexandria, Virginia, where politicians and others were gathered for a morning practice at about 7am local time.
The team was taking batting practice when a gunshot rang out and chaos erupted, politicians on the scene said.
"All of a sudden we heard a very loud shot. The gunman was over by the third base dugout with a clear view of the field," Republican Jeff Flake told CNN.
Louisiana Representative Mr Scalise was fielding balls on second base when he was shot, Mr Flake said.
He said the congressman dragged himself 10 to 15 yards into the outfield to get further away from the gunman.
Initial reports said that as many as 50 shots had been fired, but Mr Flake said "50 would be an understatement. He had a lot of ammo".
Who is Scalise?
Steve Scalise, a member of the Republican leadership in the House of Representatives, is known for his love of baseball and the late-night meals he often serves his colleagues in his office near the Capitol's ornate Statuary Hall.
Mr Scalise, the number three House Republican, was shot on Wednesday along with several others during a baseball practice in Alexandria, Virginia.
The 51-year-old distributed commemorative baseball bats to fellow members when he ran for a leadership post in 2014.
The Louisiana conservative was elected majority whip, the job of chief vote counter for the Republican leadership team.
Mr Scalise was first elected to the House in 2008 and served as chairman of the Republican Study Committee, a group of conservatives, before becoming whip in the leadership shuffle that followed the surprise defeat of then-majority leader Eric Cantor in a Republican primary.
In his whip campaign, he boasted about his conservative credentials and pointed out that he would be the only Republican leader from the South, which had a major role in giving Republicans their largest House majority in decades.
Mr Scalise, who was shot in the hip, was transported to a Washington hospital and was undergoing surgery. He is in a stable condition.
"Prior to entering surgery, the whip was in good spirits and spoke to his wife by phone. He is grateful for the brave actions of US Capitol Police, first responders and colleagues," his office said in a statement.
Mr Scalise represents a district that includes some New Orleans suburbs and bayou parishes.
Before entering Congress, he was a politician in Louisiana for eight years.
Mr Scalise faced questions last year about some of his Louisiana ties.
Six months after his election as whip, it came to light that he had spoken in 2002 to a white supremacist group founded by Ku Klux Klan leader David Duke.
Mr Scalise apologised for the speech and said he was unaware of the group's racial philosophy when he agreed to speak as a state legislator.
"I reject bigotry of all forms," Mr Scalise said then.
He and his wife, Jennifer, have two children.
Earlier: Police in Virginia have made one arrest after a senior US congressman was shot at a baseball practice.
Steve Scalise is in hospital after it happened in Alexandria this morning - his injuries aren't believed to be life-threatening.
It's understood a total of five people were hurt in the shooting.
President Donald Trump has tweeted his thoughts are with Mr Scalise, who he's described as a 'true friend'.
Rep. Steve Scalise of Louisiana, a true friend and patriot, was badly injured but will fully recover. Our thoughts and prayers are with him.— Donald J. Trump (@realDonaldTrump) June 14, 2017
Earlier:US politician, Steve Scalise, has been shot at a congressional baseball practice in Alexandria, Virginia, congressional officials said.
Mr Scalise is in a stable condition at George Washington University Hospital, a congressional aide said.
Mo Brooks, the Republican Representative for Alabama, said several other people were also hit, including two law enforcement officers.
Mr Brooks said that Mr Scalise, 51, was down on the ground with what Mr Brooks described as "a hip wound".
Louisiana Representative Mr Scalise is the number three House Republican leader.
Earlier: Police in Virginia in the US have confirmed they are investigating a shooting involving multiple people at a congressional baseball practice in northern Virginia.
The suspect in the shooting in Alexandria is variously reported to be in custody, or dead.
The shots were reported at 7.30am local time this morning near a YMCA.
Fox News has reported that the Republican party Chief Whip Steve Scalise was shot in the hip and at least one other aide was hit in the chest by a gunman with a rifle. Other reports say two police officers were also shot.
White House press secreatray Sean Spicer tweeted the president and Vice President were aware of the situation.