Mr. Shadid felt compelled to enter Syria with the help of smugglers for the same reasons that other journalists cited in interviews this week: a sense that the widespread killing and suffering there needs to be documented.

“It’s just nuts. I feel like no one there is telling the truth now,” Mr. Shadid wrote in an e-mail to editors at The Times as they weighed whether he should sneak back into the country. “We have to get the details.”

The first time he did so, in July of last year, he reported on antigovernment sentiments and sectarian tensions in the restive city of Homs. “Anthony was reporting from Homs when the rest of us could only dream of it,” said Jon Williams, the BBC world news editor, who joined others in expressing condolences to The Times on Friday.