SAN FRANCISCO When Robert F. Kennedy died in a Los Angeles hospital after being shot in a hotel kitchen by a young Palestinian, the presidential candidate’s body was flown back to New York, where it lay in repose at St. Patrick’s Cathedral for two days. A funeral Mass was held June 8.

The body was then placed in the last carriage of a 21-car train headed for Washington, where Kennedy was to be buried at Arlington National Cemetery beside his assassinated brother, John. Beside the casket, wearing a veil, sat Ethel, Bobby’s widow, pregnant with their 11th child.

When the train burst into the light after leaving Penn Station, the photographer Paul Fusco, on assignment for Look magazine, was astonished: “There were hundreds of mourners crowding together on platforms almost leaning into the train to get close to Bobby.”

Thousands of coins had been strewn on the tracks (people wanted something tangible by which to remember the day) so that there was a continuous crunching sound — one flattened presidential face after another — as the wheels turned over them.

No one will ever know the exact number, but somewhere between 1 million and 2 million people lined the tracks all the way to the District, slowing what should have been a four-hour journey to twice that time. “The train was moving mournful slow,” Michael Scott told the Baltimore Sun. He was 15 on that day.

There were other photographers on the train. But none managed to take images as beautiful, as haunting, as uncanny as Fusco’s. A selection of them makes up one part of an intense, tripartite show called “The Train: RFK’s Last Journey” at the San Francisco Museum of Modern Art.

Using two Leicas and a Nikon, Fusco took nearly 1,000 slides that day. He shot mainly in Kodachrome 64, a discontinued film noted for its dense blacks, strong contrasts and saturated colors. The images show some of the mourners — black and white, young and old, nuns, sportsmen, schoolchildren — who, on a humid summer Saturday, came out to see a train pass by.

They stood, pointing or praying. They perched on fence posts, on the roofs of vans, in tatterdemalion back yards. Bare-chested boys, shorts hitched high, stood and saluted. Couples perched with sober expressions on stationary motorcycles. Families emerged from bosky banks, baseball fields behind.

Fusco embalmed these summer scenes in an amber, liquid light. But somehow the photographs also capture a submarine disturbance. They accumulate into a portrait of a nation untethered from normality.

Just two months earlier, Martin Luther King Jr. had been murdered in Memphis. His assassination, by a racist, petty crook, triggered unrest all over the country (and the long-awaited passage of the Civil Rights Act). In Vietnam, the Tet offensive had begun. The ensuing casualties set off widespread protests. Public support for the war was beginning to collapse.

Fusco’s photographs don’t show any of this tumult. Quite the contrary. They seem, on the surface, almost Edenic. The brightly colored summer clothes of the mourners emerging from houses and standing in meadows suggest the festive mood of the Fourth of July. Instead of the dead body of a popular candidate, it could be the circus coming to town. Except that folks are weirdly still.

Their stillness is in tension with the dirgelike motion of the train, which accounts for some of the blurring that occurs in the photos, particularly around the edges. As the light dimmed over the course of that day, Fusco lengthened his exposure times accordingly, and the blur increased.

But it’s not all blur. Fusco had served in the U.S. Army Signal Corps during the Korean War, often taking photographs of the positions of enemy troops behind Chinese lines from reconnaissance aircraft. He knew how to take photographs while in motion.

On June 8, each time he clicked he made a subtle counter-motion with the camera, which helped create a pocket of focus, a bulwark against the surrounding blur. That stillness and focus feel like correlatives of the stillness, the “standing sentry,” that marks mourning all over the world.

Camera optics are one thing. They go only partway to explaining lumps in your throat. Look at these people — at what Clément Chéroux, who organized the show with Linde Lehtinen, described as “the long, sad human chain that formed along the tracks” — and you may just want to cry. (Chéroux told me that since the exhibit’s opening, many visitors have been doing just that.)

The show has two other parts. Both are inspired.

The first is by Rein Jelle Terpstra, a Dutch artist and teacher in his late 50s. As Terpstra looked at Fusco’s photographs, he noticed that many of the people they captured were holding cameras and recorders themselves. Using social media and local advertisements, he tracked down as many of the images they had taken as he could.

He turned up faded photographs, old slides, handheld video footage and even a poignant memento: a piece of red-and-blue cardboard with white stripes onto which five snapshots had been carefully mounted. Some of the slides have handwritten captions that read like lines from Samuel Beckett: “Waiting,” “Waiting and watching for the train,” “Here it comes!” and “After the train passed.”

It’s extraordinary to see Fusco’s iconic images, taken from the train, reversed and democratized in this way. Displayed along two walls traversed by a meandering line that represents the train’s southern passage, these slides and old snapshots congregate at points along the line where they were taken. Staggered in this way, they resemble fragments of faded cloth, the tattered remnants of a crumbling collective memory.

Even more arresting, however, is the show’s third and final gallery, where “June 8, 1968,” a short film by France’s Philippe Parreno, is screening. Parreno made the film in 2009, inspired by Fusco’s photographs. He uses actors to re-create the scenes Fusco saw.

Shot from a train in 70mm and accompanied by rumbling noises that intermittently cut out, the film has an atmosphere that’s both viscerally real and dreamlike. Its golden, late-afternoon tones and period details recall Terrence Malick’s “The Tree of Life.” The constant motion of the footage is like a drone note against which individual mourners — the girl in the bikini, the baseball player, the young kids — stand out in relief, because they are all utterly stationary.

Like blood cells that rush to congeal around a wound, mourners crowd together to reestablish community after death, because death is always a breach or tear in the communal fabric. What’s different about these mourners — when compared, for instance, with the recent massive crowds on the Mall — is that they don’t congregate in a big, heaving mass.

Rather, they are staggered haphazardly along a railway line. The tracks draw them toward the train, like iron filings to a magnet, but the train moves on and they remain spread out, stock-still, each individual face isolated and bewildered by grief.

The frozen poses of the Kennedy mourners remind us that on June 8, 1968, the country was in a state of deep shock.

We are still, it seems, in shock. Death by gun has become the drone note against which American life fitfully continues and, in intolerable numbers, simply cuts out. We congregate, we heal, we push for change. But for the people at the heart of it all, one thing most certainly won’t change: The people they love will not come back.

The Train: RFK’s Last Journey Through June 10 at the San Francisco Museum of Modern Art.