CHARLOTTESVILLE — Just over an hour into the train ride from Washington to West Virginia, Republican lawmakers traveling to their annual retreat were settling in for the long excursion, chatting with colleagues or family or simply stretching their legs.

Without warning, the train slammed into a white garbage truck.

"It was quite a jolt," said Rep. Tom Cole (Okla.). "It was just bam."

"You could feel we had hit something," said Sen. Mike Lee (Utah). "It took us maybe a ­quarter-mile to stop."

The force from the chartered 10-car Amtrak train sliced into the truck on the tracks Wednesday, killing one person and injuring at least five, a deadly start for a GOP gathering focused on party unity and election-year strategy.

The victim was identified as Christopher Foley, 28, of Louisa County by Albemarle County police, who said he was a passenger in the truck.

Shortly after impact, the doctors among the Republican rank and file ignored security officials' warning not to leave the train and rushed to help. Sen. Bill Cassidy (La.), a physician, along with Sen. Jeff Flake (Ariz.) and Rep. Brad Wenstrup (Ohio), helped carry one truck passenger several hundred yards to an ambulance.

They "literally pried open the doors and jumped off the train to assist those injured," said Rep. Barry Loudermilk (Ga.).

Other lawmakers quickly took to social media, tweeting to reassure family and friends that they were fine. Still others relayed information or posted video of the shattered truck and the train still on the tracks.

It was a reminder of this past summer's near-tragedy, when a gunman who targeted Republicans opened fire on a baseball field in Alexandria, Va. Then, Flake and Wenstrup, an Army combat medic, rushed to help House Majority Whip Steve Scalise (R-La.), who lay bleeding on the field and nearly died. What they did on Wednesday is "eerily familiar" to what they did last summer, Flake said. "Brad and I working like that — that was just too close."

Flake said he was struck after watching Wenstrup, for a second time in less than a year, cut away bloody clothing to tend to a gravely injured man.

"I thought after that time, 'I never want to experience a day like this again,'" he said. "Unfortunately, it came too soon."

A few passengers were "roughed up," Lee said. "Most of us hit a knee or a head on the seat in front of us, but nothing too serious."

Rep. Charles J. "Chuck" Fleisch­mann (Tenn.) — another survivor of the ballfield shooting — was nursing a hard hit to the head.

"I was on the train heading to the GOP Retreat when an accident occurred," he tweeted later. "I am OK, and working with doctors that have arrived."

Rep. Jason Lewis (Minn.), who also hit his head, was seen on television footage being transported to an ambulance. An aide said Lewis was treated for a concussion and released.

Among those tending to the victims was a husband-and-wife team — Rep. Larry Bucshon (Ind.), who was a practicing cardiothoracic surgeon before joining Congress, and Kathryn Bucshon, an anesthesiologist. The doctors on the scene quickly determined one man was dead, and the Bucshons joined the doctors tending to the other man, who was suffering from severe head and facial injuries.

Wenstrup was holding the man's head to help him breath, while another lawmaker held his legs up to aid circulation.

The Bucshons started efforts to maintain an airway. "Even though he was breathing, in situations like that, you never know when they're going to obstruct and not be able to breathe," Larry Bucshon said.

Kathryn Bucshon said she attempted to intubate the man using equipment from the EMTs who had arrived on the scene. After two attempts failed, she said, "They were ready to move him. We put in an oral airway" — a plastic device that keeps the mouth open — "he was breathing, and we thought it best to get him to the hospital."

"I wish we could have done more for them," she said.

The day began on a chilly morning at the Capitol. Hours after President Trump's State of the Union address, House and Senate Republicans had boarded separate charter buses that carried them a few blocks to Union Station.

Amtrak Police watched closely as the group processed toward Gate G — resembling any other band of casual travelers. Rep. Sean P. Duffy (Wis.) had his wife and eight children in tow. Rep. K. ­Michael Conaway (Tex.) wore a red baseball cap. Rep. Dana Rohrabacher (Calif.) was carrying his guitar.

"Last night was a big night for us, and we were all very happy on the train," said Rep. Phil Roe (Tenn.), a retired physician who was among those to tend to the injured. "And just in a millisecond, how that changed, the mood of everything."

Their destination was West Virginia's Greenbrier Resort, once home to secret government facilities built in the event of a nuclear attack that now often hosts the winter conferences held by Democrats and Republicans to plot strategy. Republicans opted to travel together by rail for security and logistical purposes. Speaker Paul D. Ryan (Wis.) was on the train and uninjured; Senate Majority Leader Mitch McConnell (Ky.) was not on board. Republicans were scheduled to arrive by early afternoon.

The crash occurred in Crozet, Va., a town of about 5,500 residents 12 miles west of Charlottesville. Residents who live near the crash site said it's not the first time vehicles have struggled at the ­Lanetown rail crossing.

The crossing "is not good for trucks of any size," said Ray Page McCauley Jr., who said that the height of the crossing has long posed problems and that he's seen other trucks get stuck before.

"A lot of tractor-trailers have gotten stuck, and even limos seem to have trouble getting across it," he said. "If a truck breaks down, there isn't enough time to call the railroad to let them know."

Back on the train, most passengers had a clear view of the truck.

"It's been maybe cut in half," Lee said. "We can see garbage strewn around, and we can see the back half of the truck."

Others onboard stood with U.S. Capitol Police officers concerned that the damaged truck could cause a gas explosion — or that something more nefarious might unfold.

Initially, "the physicians couldn't get out because there was concern about an explosion," said Rachel Campos-Duffy, the congressman's wife, who called into Fox News, where she is a contributor.

"I could see the CPR going," she told Fox, "but sadly one of them was lost."

Speaking by telephone from the scene, Flake confirmed that one passenger in the truck had died. Two others were injured. The body was covered by a blue tarp.

"They never could revive him — they tried for quite awhile," he said. The passenger he and others carried to an ambulance "was breathing but is in pretty bad shape."

By 1:37 p.m., the train had backed into the Charlottesville station as 10 charter buses pulled into the parking lot. Police officers quickly cordoned off the station, keeping away reporters and onlookers. Members began to climb off the trains, many carrying their own luggage. Many were somber as they reflected on the injuries suffered by the truck passengers.

Sen. Rob Portman (Ohio) got off with his wife, Jane, and waiting for them was their son, Jed. He's a University of Virginia student who had come over from the nearby campus to say hello. Portman described a "very, very sad" experience, adding: "Prayers are with the three and their family."

Across the street from the train station at Mel's Cafe, Greg Snyder, 69, couldn't believe the scene.

"We can't stay out of the news," he said, referencing the city's race riots last August.

Frank Larkin, the Senate sergeant at arms, drove down from Washington to Charlottesville when he got word of the crash. He said it appeared to be an "unfortunate accident" without criminal intent but that an investigation would continue.

"It certainly tests our mettle and our preparedness," Larkin said of tragedy confronting Congress.

By 2:28 p.m., the charter buses started leaving Charlottesville. Slightly bruised and behind schedule, Republicans vowed to get back to work.

Wenstrup said instinct took over in the initial moments after the collision. But afterward, the gravity of what had happened sank in on him.

"When you start thinking about what could have happened, I think that that's makes it even tougher," he said. "We had a fatality and that is bad enough, but when I think about the fact that this train did not derail and that everybody really on board was good, that gives me great solace compared to what it could have been."

O'Keefe reported from Washington. Erica Werner and Sean Sullivan in Charlottesville, Lori Aratani in Washington and Hawes Spencer in Crozet contributed to this report.