Pablo Ramirez was living his dream in San Francisco. The native of New York came to the city with his skateboard and made a name for himself as one of the fastest skaters on the famously steep hills. His stunts were death-defying.

That all ended in tragedy on Tuesday when the 26-year-old was fatally struck by a dump truck while skateboarding up Seventh Street in the city’s South of Market neighborhood. Witnesses said Ramirez was hanging onto the back of a moving vehicle and being towed just moments before he was killed, police said.

His death sent shock waves through the San Francisco skateboarding community. As his friends learned what happened, they converged on the scene, crying and hugging while news of Ramirez’s death spread on social media.

“He was one of the happiest, most positive people I have ever met,” said Tony Vitello, the owner of Thrasher magazine. “He was just exploding with energy, overflowing with life. It was infectious. He would just be so pumped up to see you. He was just that stoked all the time.”

Ramirez was born in New York and moved to San Francisco to skate, Vitello said. He was sponsored and skated with the GX-1000 group, a crew of skateboarders known for bombing hills and described in GQ magazine as the “most fearless crew in skateboarding.”

The 2018 magazine article, which featured Ramirez modeling designer clothing, described his death-defying moves and called him one of “the fastest people who have ever skated” in San Francisco.

“Pablo will go straight through a red light and not even look at all,” skateboarder and filmmaker Ryan Garshell told GQ. “It’s up to the driver to stop, and if they don’t stop, that’s it. Somehow he always makes it. It’s really magical.”

On Tuesday morning, Ramirez was among a crowd who packed a courtroom at the Hall of Justice to support fellow skateboarder Jesse Vieira. The 24-year-old Vieira is on trial for charges of assault with a deadly weapon and battery for an alleged skateboard attack in November that left a security guard with a traumatic brain injury.

Dan Jansen, 57, now has a large crater in his head from where doctors removed part of his skull and brain, following an altercation with Vieira and other skaters outside the Bank of America center at 555 California St. in the city’s Financial District.

Vieira was arrested in December and his friends — including Ramirez — have packed the courtroom for each of the young man’s hearings, while Jansen’s family members filled the other side. Vieira’s trial began this week.

Shortly before noon, the judge ordered a recess for lunch. Ramirez died around 12:15 p.m., roughly four blocks from the courthouse, police said.

Paramedics found him unconscious, his twisted body bleeding in the middle of Seventh Street between Natoma and Minna streets. They attempted to revive him, but he was pronounced dead at the scene, police said.

Ramirez’s body was covered with a yellow tarp just feet from his overturned skateboard and a single orange sneaker that was knocked off in the collision. Nearly a dozen of his friends watched in horror, many doubled over in grief, as the medical examiner loaded his body into a white van.

Investigators were speaking with witnesses and gathering security video as they worked to determine what happened in the moments before the fatal collision. The truck driver remained at the scene and was cooperating with investigators. Police do not suspect drugs or alcohol were factors in the wreck.

The truck had markings reading UPC Hauling, a South San Francisco company that dissolved in 2018, according to records. Attempts to reach the truck’s registered owner were unsuccessful.

Ramirez, known on Instagram as “Psplifff,” posted his last skateboard video four days ago. On Tuesday the comment section — he had nearly 30,000 followers — was full of tributes. One called him “King of your time.” Another read, “Ride on brother, you will always be one of the fastest to ever do it.”

Ramirez, who was also a DJ and painter, previously traveled to Russia with a group from Thrasher. Last summer he went to the Dominican Republic, where his family was originally from. He posted videos of his time there.

“He was so excited to skate there,” Vitello said. “He loved the architecture and how colorful it was. He was stoked to go back there and skate.”

When Thrasher Editor Jake Phelps died in March, Vitello received hundreds of letters, texts and calls offering condolences. Among the outpouring of grief, Ramirez’s words stood out as among the most profound.

“His was the most beautiful exchange that I heard about Jake’s passing,” he said. “He talked about everything Jake had given to us and how we were going to give it back to Jake. He was a San Francisco guy through and through, even though he had only been here a few years.”

Phelps and Ramirez were “two guys who lived without hesitation,” he said.

Tuesday’s deadly accident happened a little more than a block from where a truck crushed bicyclist Tess Rothstein last month. A driver opened her door into the bike lane at Sixth and Howard streets, prompting the 30-year-old Rothstein to swerve into the truck.

Ramirez’s death marks the 11th person to be killed by a vehicle this year in San Francisco. Seven pedestrians, including Ramirez, one bicyclist and three people in vehicles have been killed, police said.

Evan Sernoffsky and J.K. Dineen are San Francisco Chronicle staff writers. Email: esernoffsky@sfchronicle.com, jkdineen@sfchronicle.com Twitter: @EvanSernoffsky, ASFjkdineen