BEIRUT, Lebanon — The Rev. Frans van der Lugt, a Dutch Jesuit priest who became a symbol of suffering and compassion in the war-ravaged Old City district of Homs, Syria, was shot to death Monday morning by a lone gunman, according to members of his order. The killing came amid growing disputes between Syrian insurgents blockaded in the Old City — those who want to accept an amnesty from the government in exchange for laying down their arms, and those who do not.

After Syrian government forces isolated and laid siege to the rebel-held Old City for more than a year, a truce in January allowed the evacuation of 1,500 people, both civilians and fighters. But Father Frans, as he was known, insisted on remaining in the monastery where he had lived for decades, offering refuge to Muslim and Christian families alike and sharing their deprivation and trauma.

The killer’s identity and motives were not known, but the attack carried a heavy symbolic importance. Though he was European, Father Frans, 75, had come to be considered part of Syrian society and was well known in and around Homs, including among local insurgents in the Old City. He survived there long after foreign fighters from the Islamic extremist group Nusra Front moved in and raised new fears for the few Christians who remained.

But now, something had changed, and he could no longer be protected. Fingers quickly pointed in all directions.

“The death of the priest is a scandal for the rebels,” said Mahmoud Taha, an antigovernment activist in Talbiseh, a village near Homs where the Jesuits run a center for the elderly. Mr. Taha speculated that the local Homs fighters had become radicalized. “They no longer accept anyone but those who are like them,” he said.

The Syrian exile opposition coalition said in a statement that Father Frans was protected by rebels, including a guard from the Free Syrian Army who was shot in the chest in the attack.

Amir Bader, an antigovernment activist in the Old City, said most of the fighters did not regard the priest as an enemy.

“Maybe some fanatic shot him,” Mr. Bader said, “or some regime associate did it, so the regime will show all the Christians: ‘Look what will happen to any of you if you support the revolution like Father Frans.' ”

Syrian Christians have not been of one mind about the conflict in their country, which began with mass protests in 2011. Some have expressed sympathy with the protesters, while Christian leaders at first sought to stay neutral. But many Christians, seeing Islamist extremists gaining power within the insurgency, have increasingly stuck with the government of President Bashar al-Assad.

At the same time, figures like Father Frans could be an inconvenience for the government. Jesuits have continued to aid people in Syria regardless of their politics, an act that the Jesuit workers describe as humanitarian neutrality, but that some government supporters view with suspicion. Another foreign-born Jesuit who made his home in Syria, the Rev. Paolo Dall’Oglio, fell out with the government early in the conflict; he was kidnapped almost a year ago, it is believed, by extremist fighters.

Father Frans expressed doubts about the government’s opponents in a letter to the website of a Dutch group favoring the Syrian government in January 2012. “Most Syrians do not support the opposition,” he wrote. “Therefore, you cannot say that this is a popular uprising.” Brenda Stoter Boscolo, a Dutch journalist, said Father Frans still said he felt that way in 2013, after the government had bombarded the Old City for months.

At least until recently, most of the insurgents there were believed to be locals. But the amnesty in January applied only to Syrians, so the evacuation probably reduced the number of homegrown fighters in the Old City — who were more likely to protect Father Frans — but not the number of foreign fighters.

Mr. Bader said Father Frans was killed by a masked man who entered the monastery in Bustan al-Diwan, a Christian part of the Old City.

The secretary of the Dutch Jesuit Order, Jan Stuyt, gave a slightly different version in remarks to Agence France-Presse. “A man came into his house, took him outside and shot him twice in the head, in the street in front of his house,” Mr. Stuyt was quoted as saying.

He said there were no known specific threats against the priest, who will be buried in Syria “according to his wishes.”

Individual deaths are often lost sight of in a war that has claimed more than 150,000 lives, and opponents of the government have sometimes complained that the plights of foreigners or members of religious minorities in the country get more attention than those of other Syrians. Indiscriminate government bombing kills people daily in the northern city of Aleppo and other places around the country. Nearly every Syrian family seems to include someone who has been killed, wounded, kidnapped or detained.

Still, the killing of Father Frans struck a chord, because he chose voluntarily to share the plight of the people who stayed in the Old City. People who have left the besieged neighborhood say that most of those still there are fighters, but some are civilians who refuse to leave their homes, doubtful of government promises of safety and unwilling to give up all they have.

“It was his choice to stay there,” a Syrian Jesuit priest who has worked with refugees and is still in the country said in a telephone interview, sounding dejected and asking not to be identified to protect his safety.

Father Frans spoke movingly of the suffering in the Old City in a video plea for aid that was posted online in January. “There is nothing harder than seeing parents in the street looking for food for their children,” he said in the video, which gained wide attention. “We do not want to die,” he said.

Father Frans was fluent in Arabic and was trained in psychotherapy. He founded the Al Ard Center outside Homs, which cared for disabled people and fostered dialogue among people of different religions. The center took in displaced people well into the civil war, though the staff eventually left because, they said, they could not assure the safety of their guests.

Father Frans explained his decision to remain in the Old City in an interview published in February on ReliefWeb, a website focusing on humanitarian organizations.

“I don’t see Muslims or Christians, I see, above all, human beings,” he said, who “hunger to lead a normal life.” As the only priest left in the Old City to help the people there with their suffering, he said, “how can I leave? This is impossible.”

Besher al-Hamwi, a Syrian now living in France, recalled hiking with Father Frans in Syria before the civil war, and shared photos of the priest chatting affectionately with young Syrians in a meadow. “He was kind,” he said. “It’s a loss first for the Syrians, then for the Netherlands.”