A rifle-wielding opponent of President Donald Trump opened fire on US lawmakers practising for a charity baseball game in the Washington suburb of Alexandria, Virginia yesterday, wounding a top Republican congressman and four others before he was fatally injured in a shootout with police.
The 66-year-old gunman was identified as James T Hodgkinson of Belleville, Illinois, an ardent supporter of left-wing Senator Bernie Sanders. He later died of his injuries, reports AFP.
Sanders said he was "sickened" by what he called a "despicable act".
Congressman Steve Scalise, the number three Republican in the House of Representatives, was expected to recover after being shot in the hip.
Four others were wounded: a congressional aide, a lobbyist and two Capitol Police officers.
In a separate incident, at least four people, including the suspected gunman, were killed. The suspect, a disgruntled employee of United Parcel Service Inc, opened fire at a company package sorting hub in San Francisco, two local TV news stations reported.
After firing on co-workers, he turned a gun on himself when confronted by police, according to NBC Bay Area and ABC 7. He later died at an area hospital, they said, citing law enforcement sources.
San Francisco police said the building was secure but offered no immediate information on victims.
In an address to the nation, Trump appealed for unity following the early morning assault, which came amid high political tension in the US capital after a vitriol-filled 2016 election.
Trump described Scalise as a "very good friend," a "patriot" and a "fighter".
FBI agent Tim Slater told a news conference that investigators were still "exploring all angles" and that it was too early to tell if the Republican lawmakers were deliberately targeted.
He would also not confirm a report by CBS that the gunman used a high-powered semi-automatic assault rifle.
According to his Facebook page, Hodgkinson was a fervent supporter of Sanders, the feisty independent who battled Hillary Clinton for the Democratic presidential nomination last year.
Hodgkinson's social media posts displayed strong anti-Trump sentiment.
"I know he wasn't happy with the way things were going, the election results and stuff," his brother, Michael Hodgkinson, told The New York Times. But he said news of the shooting came "totally out of the blue."
Sanders swiftly responded to reports that the suspect had volunteered on his presidential campaign.
"I am sickened by this despicable act," he said.
"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."
The shooting took place around 7:00am (1100 GMT) as the Republican team practised for the charity game, a well-loved showdown between Senate and House members of both the Republican and Democratic camps.
Congressman Rodney Davis told CNN he was up at bat at the time, and Scalise was in the field at second base.
"I was batting, we heard a loud noise.... The next thing I remember was somebody on the field yelling 'Run, he's got a gun.'"
Alexandria Police Chief Michael Brown said his officers arrived at the scene within three minutes, engaged the suspect together with Capitol Police officers, and took him into custody. He later died from his wounds.
Trump praised the "heroic" acts of law enforcement in subduing the shooter.
"Many lives would have been lost if not for the heroic actions of the two Capitol Police officers who took down the gunman despite sustaining gunshot wounds during a very, very brutal assault," he said.
Senator Rand Paul, also at the practice, said he believed the rapid intervention narrowly prevented a bloodbath.
"It would have been a massacre. And having no self-defence, the field was basically a killing field," Paul told reporters.
Scalise's office said the 51-year-old was in stable condition at a Washington hospital after being shot in the hip.
Scalise, a representative from the southern state of Louisiana elected to Congress in 2008, heads the conservative House caucus known as the Republican Study Committee.
The staunch conservative is among the lawmakers leading the drive to repeal former president Barack Obama's signature health care law, among other top Republican priorities.