An Oscar winner and multiple nominee, Hoffman could take on any character with almost unnerving authority, whether the religious leader in command of his every word in "The Master," a trembling mess in "Boogie Nights," or the witty, theatrical Truman Capote in "Capote."
Fearless in his choices, encyclopedic in his preparation, he was a Shakespearean performer in modern dress, bringing depth and variety to charlatans, slackers, curmudgeons and loners.
"Hearing that Philip Seymour Hoffman passed away came as much as a shock to me as to anyone else I'd imagine," said Anton Corbijn, director of "A Most Wanted Man," one of two films (the other being "In God's Pocket") starring Hoffman that premiered last month at the Sundance Film Festival.
He was not only the most gifted actor I ever worked with," Corbijn added, "he had also become an incredibly inspiring and supportive friend."
Friends, peers, family members and his countless fans were in grief after Hoffman was found in his Greenwich Village apartment with what law enforcement officials said was a syringe in his arm.
The two officials told The Associated Press that glassine envelopes containing what was believed to be heroin were also found with Hoffman. Those items are being tested.
The law enforcement officials, who spoke to The Associated Press on condition of anonymity because they are not authorized to speak about evidence found at the scene, said the cause of death was believed to be a drug overdose.
(Read more: Philip Seymour Hoffman found dead)
Police will only say the investigation is continuing. An autopsy is planned for Monday, according to medical examiner spokeswoman Julie Bolcer.
Besides his Oscar win for "Capote," the stage-trained Hoffman received four Academy Awards nominations and several nominations for theater awards, including three Tonys. He was equally acclaimed and productive, often appearing in at least two to three films a year, while managing an active life in the theater. He had been thriving for more than 20 years and no one doubted that a long, compelling run awaited him.
Like Laurence Olivier or Meryl Streep, his appeal was not bound by age or appearance or personality. He was not an actor whom audiences turned to for youth and romance. Heavy set with a lumpy build and limp, receding blond hair, he was a character actor with the power to play the lead, in movies that screened in both art houses and multiplexes.
"No words for this. He was too great and we're too shattered," said Mike Nichols, who directed Hoffman in "Charlie Wilson's War" and on stage in "Death of a Salesman."
Hoffman spoke candidly over the years about past struggles with drug addiction. After 23 years sober, he admitted in interviews last year to falling off the wagon and developing a heroin problem that led to a stint in rehab.
The law enforcement officials said Hoffman's body was discovered in a bathroom at his Greenwich Village apartment by a friend who made the 911 call and his assistant.
Late Sunday, crime-scene technicians carrying brown paper bags went in and out of Hoffman's building as officers held back a growing crowd of onlookers.
Hoffman's family called the news "tragic and sudden."
"We are devastated by the loss of our beloved Phil and appreciate the outpouring of love and support we have received from everyone," the family said in a statement.
With a range and discipline more common among British performers than Americans, Hoffman was convincing whether comic or dramatic, loathsome or sympathetic, powerless or diabolical.
In one of his earliest movie roles, he played a spoiled prep school student in "Scent of a Woman" in 1992. A breakthrough came for him as a gay member of a porno film crew in "Boogie Nights," one of several movies directed by Paul Thomas Anderson that Hoffman would eventually appear in. He played comic, off-kilter characters in "Along Came Polly" and `'The Big Lebowski." He bantered unforgettably with Laura Linney as squabbling siblings in "The Savages." He was grumpy and idealistic as rock critic Lester Bangs in "Almost Famous." He was grumpy and cynical as baseball manager Art Howe in "Moneyball."
In "The Master," he was nominated for a 2013 Academy Award for best supporting actor for his role as the charismatic, controlling leader of a religious movement. The film, partly inspired by the life of Scientology founder L. Ron Hubbard, reunited the actor with Anderson.
He also received a 2009 supporting nomination for "Doubt," as a priest who comes under suspicion because of his relationship with a boy, and a best supporting actor nomination for "Charlie Wilson's War," as a CIA officer.
Many younger moviegoers know him as the scheming Plutarch Heavensbee in "The Hunger Games: Catching Fire" and he was reprising that role in the two-part sequel, "The Hunger Games: Mockingjay," for which his work was mostly completed. The films are scheduled for November 2014 and November 2015 releases.
Just weeks ago, Showtime announced Hoffman would star in "Happyish," a new comedy series about a middle-aged man's pursuit of happiness.
Born in 1967 in Fairport, N.Y., Hoffman was an athletic boy, but a neck injury sustained while wrestling ended any hopes for a career in sports. He soon became interested in acting, mesmerized at 12 by a local production of Arthur Miller's "All My Sons." He studied theater as a teenager with the New York State Summer School of the Arts and the Circle in the Square Theatre. He then majored in drama at New York University.
In his Oscar acceptance speech for "Capote," he thanked his mother for raising him and his three siblings alone, and for taking him to his first play. Hoffman's parents divorced when he was 9.
On Broadway, he took on some of the stage's most ambitious parts—Willy Loman in "Death of a Salesman," Jamie in "Long Day's Journey Into Night" and both leads in "True West." All three performances were Tony nominated.
Last year, Hoffman crossed to the other side of the footlights to direct Bob Glaudini's "A Family for All Occasions" for the Labyrinth Theatre Company, where he formerly served as co-artistic director. Hoffman has also directed "Jesus Hopped the A Train" and "Our Lady of 121st Street" for the company and received Drama Desk Award nominations for both productions.
Hoffman is survived by his partner of 15 years, Mimi O'Donnell, and their three children.