It might have been one of the most talked about television events in recent years: James Gandolfini was coming home to HBO in a new series, his first since his indelible portrayal of the mob boss Tony Soprano on “The Sopranos.”
His sudden death Wednesday in Italy at 51 has cut short that tantalizing prospect — though there remains a chance that Mr. Gandolfini’s work in the show, a tense crime thriller called “Criminal Justice,” may yet be seen.
It would be just a hint of what might have been, because Mr. Gandolfini makes only a brief, though arresting, appearance in the show’s pilot, playing a distinctly different character from Tony, a shambling lawyer looking for needy clients in jailhouses.
Friends and colleagues expressed deep personal sadness on Thursday at the death of Mr. Gandolfini. He was staying at the Boscolo Exedra Roma Hotel on Wednesday when he experienced a medical emergency at about 10 p.m. that night, said Laura Conti, the hotel’s marketing and communication manager.
Ms. Conti said in a statement that hotel personnel “notified the emergency crews, who administered first aid before taking Mr. Gandolfini to the hospital, where he died of an apparent heart attack.”
Mr. Gandolfini was taken to the Policlinico Umberto I hospital in Rome. After additional attempts to revive him, he was pronounced dead at 11 p.m., Dr. Claudio Modini, the head of the hospital’s emergency room, told The Associated Press. Italian law required that an autopsy would be conducted 24 hours after his death, The A.P. said.
Mr. Gandolfini’s death left the creator of “The Sopranos,” David Chase, very emotional, he said. “There was a 14-year-old boy in there,” Mr. Chase said of the actor. “I don’t mean that’s how he behaved, though sometimes he did — sometimes he behaved like he was 5 years old, sometimes he behaved like an 85-year-old savant.”
But, he continued, Mr. Gandolfini exhibited the quality of a boy “encountering the world for the first time and it was all starting to come together — and it’s not all good news.”
He added, “There was something about his eyes, something in there that you wanted to nurture.”
When it came to “The Sopranos,” Mr. Chase said: “We both sort of got out of that show with our lives. It was a roller coaster.”
They worked together again, on “Not Fade Away,” released last year. Calling that collaboration “a blessing,” Mr. Chase said that “I would have loved to work with him again and again,” and that “He had a tremendous amount of good work left in him.”
Edie Falco, who memorably played Tony’s long-suffering wife, Carmela, issued a statement on Thursday, saying she would “hold on to the memories of our intense and beautiful time together.”
“The love between Tony and Carmela was one of the greatest I’ve ever known,” she said.
But those he worked with also expressed regret for the missed opportunity to see Mr. Gandolfini continue what had become a busy career as both performer and producer.
Mr. Gandolfini would have been an executive producer of “Criminal Justice,” and through his production company, he leaves behind a batch of other prospective projects, including another HBO drama he might have starred in, “Big Dead Place,” set in Antarctica. His company also sold a script to CBS for a comedy called “Taxi 22,” which HBO had rejected.
On the movie side, Mr. Gandolfini had only recently finished working on two still-unreleased films for Fox Searchlight Pictures. He has a starring role, opposite Julia Louis-Dreyfus, in a romantic comedy, “Enough Said,” which was directed by Nicole Holofcener and was shot in Los Angeles last summer. And he played a supporting role in “Animal Rescue,” a crime drama, which was directed by Michaël R. Roskam, and shot in New York in March and April this year.
Both films are expected to open in 2014, and neither appears to have needed further production work from Mr. Gandolfini, Angela Johnson, a spokeswoman for Fox Searchlight, said on Thursday.
Michael Cieply and Dave Itzkoff contributed reporting.