US president Donald Trump has visited critically-ill party whip Steve Scalise, who was shot by a rifle-wielding attacker as he practised for a charity baseball game.
Mr Trump spoke to the House of Representatives majority whip's family during a visit to MedStar Washington Hospital Centre on Wednesday evening.
The president and his wife Melania spent about half an hour at the hospital, where White House press secretary Sean Spicer described the scene in the intensive care unit as "emotional".
Mr Spicer said the president was also briefed by Mr Scalise's medical team, met Capitol Police officer Crystal Griner, who was shot in the ankle during the attack in Alexandria, Virginia, and thanked police who gathered at the hospital.
The president was accompanied by White House doctor Ronny Jackson.
The gunman, identified as James Hodgkinson, 66, opened fire on Republicans as they practised for the baseball game on Wednesday, critically wounding Louisiana member Mr Scalise, 51, and hitting aides and police as congressmen and others dived for cover.
The assailant, who had nursed grievances against Mr Trump and the Republican Party, fought a gun battle with police before he was shot and later died.
Colleagues said Mr Scalise had been fielding at second base at a local park in Alexandria, just across the Potomac River from the nation's capital, as the Republicans practised for their annual game with Democrats.
He dragged himself away from the infield, leaving a trail of blood before colleagues could rush to his assistance.
He was in a critical condition Wednesday night and doctors said he would need several more operations.
Hodgkinson, a home inspector from Illinois, had several minor run-ins with the law in recent years and belonged to a Facebook group called Terminate the Republican Party.
He had been living out of his van in the Alexandria area in recent months, the FBI said.
Capitol Police officers who were in Mr Scalise's security detail wounded the gunmen, who later died of his injuries, Mr Trump told the nation from the White House.
"Everyone on that field is a public servant," the president said.
"Their sacrifice makes democracy possible."
Politicians noted their good fortune in having armed protectors on hand.
"Thank God," they exclaimed over and over, and said otherwise the shooter would have been able to take a huge deadly toll.
The events left the capital horrified and stunned and prompted immediate reflection on the current hostility and vitriol in American politics.
Politicians called for a new dialogue on lowering the partisan temperature and Mr Trump urged Americans to come together as he assumed the role of national unifier for one of the first times in his presidency.
House of Representatives proceedings were cancelled for the day and instead speaker Paul Ryan of Wisconsin and Democratic leader Nancy Pelosi of California issued their own calls for unity.
"An attack on one of us is an attack on all of us," Mr Ryan said, to prolonged applause.
Shortly after the shooting, Bernie Sanders, the former candidate for the Democratic presidential nomination, said on the Senate floor that the gunman was apparently a volunteer for his campaign last year.
Mr Sanders said he condemned the violence "in the strongest possible terms".
Mr Scalise the number three House Republican leader, was first elected in 2008.
The popular and gregarious member is known for his love of baseball and handed out commemorative bats when he secured the job of House whip several years ago.
Texas congressman Roger Williams said one of his aides, Zack Barth, was shot but was doing well and expected to recover fully.
Two police officers sustained relatively minor injuries and a former congressional aide was taken to hospital.
The shooting happened at a popular park and baseball complex where Republican members and others were gathered for the morning practice at about 7am.
They were in good spirits despite the heat and humidity as they prepared for the annual congressional baseball match that pits Republicans against Democrats.
The popular annual face-off, which raises money for charity, is scheduled for Thursday evening at Nationals Park across the Potomac River in Washington, and will take place as planned.
Hodgkinson had been in the area since March, living out of his van, said Washington FBI special agent in charge Tim Slater.
Former Alexandria mayor Bill Euille, a Democrat, said he had often spoken to him on recent mornings at the nearby YMCA.
Hodgkinson's apparent Facebook page included strong criticism of Republicans and the Trump administration.
But Mr Slater said authorities were still working to determine a motive and had no indication Hodgkinson knew about the baseball practice ahead of time.
The event has raised questions about the security of members of Congress.
While the top members, including Mr Scalise, have security, others do not and regularly appear in public without protection.
The last time a politician was shot was when Democrat Gabby Giffords of Arizona was hit in the head and gravely injured while meeting constituents at a supermarket car park in 2011.
After the Giffords shooting, politicians have held fewer open town halls and have been advised to increase security at such events.