Shadid, shot in the West Bank in 2002 and kidnapped for six days in Libya last year, apparently died of an asthma attack, The Huff Post said.
Tyler Hicks, a Times photographer who was with Mr. Shadid, carried his body across the border to Turkey.
According to The New York Times, the exact circumstances of Mr. Shadid’s death and his precise location inside Syria when it happened were not immediately clear.
Mr. Hicks said that Mr. Shadid, who had asthma and had carried medication with him, began to show symptoms as both of them were preparing to leave Syria on Thursday, and the symptoms escalated into what became a fatal attack.
Hicks told the newspaper that Shadid suffered one bout of asthma the first night, followed by a more severe attack a week later on the way out.
“I stood next to him and asked if he was O.K., and then he collapsed,” Mr. Hicks said. “He was not conscious and his breathing was very faint and very shallow.” After a few minutes, he said, “I could see he was no longer breathing.”
Hicks said that Shadid was not conscious and that his breathing was “very faint” and “very shallow.” He said that after a few minutes he could see that Shadid “was no longer breathing.”
Shadid’s father, Buddy Shadid, told The Associated Press on Thursday his son had asthma all his life and had medication with him.
“(But) he was walking to the border because it was too dangerous to ride in the car,” the father said. “He was walking behind some horses – he’s more allergic to those than anything else – and he had an asthma attack.”
Shadid, a 43-year-old American of Lebanese descent, had a wife, Nada Bakri, and a son and a daughter.
His death abruptly ended one of the most storied careers in modern American journalism.
Mr. Shadid began his Middle East reporting career as a correspondent for The A.P. based in Cairo, traveling around the region from 1995 to 1999.
He later worked at The Boston Globe before moving to The Post, where he was the Islamic Affairs correspondent and Baghdad bureau chief. He joined The Times at the end of 2009.
He had worked previously for the AP, The Washington Post and The Boston Globe.
He won Pulitzer Prizes for international reporting in 2004 and 2010 for his Iraq coverage.
In the 2004 citation, the Pulitzer Board praised “his extraordinary ability to capture, at personal peril, the voices and emotions of Iraqis as their country was invaded, their leader toppled and their way of life upended.”
In the 2010 citation, the board praised “his rich, beautifully written series on Iraq as the United States departs and its people and leaders struggle to deal with the legacy of war and to shape the nation’s future.”
In 2002, while working for The Globe, he was shot and wounded in the shoulder as he walked on a street in Ramallah, in the Israeli-occupied West Bank.
During the tumultuous protests in Cairo last year that led to the fall of President Hosni Mubarak, Mr. Shadid was hounded by Mr. Mubarak’s police, and during a police raid, he had to hide the computers used by Times reporters.
“Anthony was one of our generation’s finest reporters,” Times Publisher Arthur Sulzberger said in a statement.
“He was also an exceptionally kind and generous human being. He brought to his readers an up-close look at the globe’s many war-torn regions, often at great personal risk. We were fortunate to have Anthony as a colleague, and we mourn his death,” he said.
Mr. Shadid’s final article for The Times, which ran on Feb. 9, was a behind-the-scenes look at the tumultuous situation in Libya, where rival militias had replaced the government of Col. Muammar el-Qaddafi.
According to The New York Times, Mr. Shadid also had a penchant for elegiac prose. In the opening of a new book, “House of Stone,” to be published next month, he described what he had witnessed in Lebanon after Israeli air assaults in the summer of 2006:
“Some suffering cannot be covered in words,” he wrote. “This had become my daily fare as reporter in the Middle East documenting war, its survivors and fatalities, and the many who seem a little of both. In the Lebanese town of Qana, where Israeli bombs caught their victims in the midst of a morning’s work, we saw the dead standing, sitting, looking around. The village, its voices and stories, plates and bowls, letters and words, its history, had been obliterated in a few extended moments that splintered a quiet morning.”