ALEXANDRIA, Va.  — A rifle-wielding attacker opened fire on Republican lawmakers as they practiced for a charity baseball game Wednesday, critically wounding House GOP Whip Steve Scalise of Louisiana and hitting aides and Capitol police as congressmen and others dove for cover. The assailant, who had nursed grievances against President Donald Trump and the GOP, fought a running gun battle with police before he, too, was shot and later died.

Colleagues said Scalise, who had been fielding balls at second base, dragged himself away from the infield leaving a trail of blood before they rushed to his assistance. He was listed in critical condition, but his office said that before he underwent surgery for a wound in his hip he was in good spirits and spoke with his wife by telephone.

The shooter was identified as James T. Hodgkinson, a 66-year-old home inspector from Illinois who had several minor run-ins with the law in recent years and belonged to a Facebook group called “Terminate the Republican Party.”

Capitol Police officers who were in Scalise’s security detail wounded the shooter, who was taken into custody. He later died of his injuries, Trump told the nation from the White House.

“Everyone on that field is a public servant,” Trump said, his tone somber, America’s acrimonious politics set aside for the moment. “Their sacrifice makes democracy possible.”

Lawmakers 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.

Across the Potomac River in Washington, the shocking events left the Capitol horrified and stunned, and prompted immediate reflection on the current hostility and vitriol in American politics. Lawmakers called for a new dialogue on lowering the partisan temperature, and Trump urged Americans to come together as he assumed the role of national unifier for one of the first times in his presidency.

Proceedings were canceled for the day in the House, 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,” 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 shooter apparently was a volunteer for his campaign last year. Sanders said he denounced the violence “in the strongest possible terms.”

Scalise, 51, the No. 3 House Republican leader, was first elected in 2008. The popular and gregarious lawmaker is known for his love of baseball and handed out commemorative bats when he secured the job of House whip several years ago.

Texas Rep. Roger Williams said that one of his aides, Zack Barth, was shot was doing well and expected to fully recover. Two Capitol Police officers sustained relatively minor injuries. A former congressional aide was hospitalized.

The shooting occurred at a popular park and baseball complex in Alexandria, Virginia, where Republican lawmakers and others were gathered for a morning practice about 7 a.m.