For days, the news that someone might be killing Muslim men in Albuquerque spread fear among the city’s Muslim residents, some of whom were so afraid of becoming the next target that they fled town or hunkered down in their homes.

On Tuesday, the police said they had arrested a man who was himself Muslim and who may have targeted at least two of the victims because he was angry that his daughter had married a man from the other major branch of Islam.

The police said the man, Muhammad Syed, 51, would be charged in two of the killings and that he was a suspect in the other two deaths.

Ahmad Assed, the president of the Islamic Center of New Mexico, a mosque that at least three of the victims had attended, said he understood that the authorities were looking at the possibility that the suspect was a Sunni Muslim who may have been motivated by resentment over a marriage to a Shiite Muslim.

He and the police cautioned that details remained sparse, and Mr. Assed noted that at least one of the victims was Sunni.

Police officials said they were not yet sure if a dispute over a marriage was the sole motive, but said they were aware of it and had found evidence that an “interpersonal conflict” may have led to the shootings. Chief Harold Medina of the Albuquerque Police Department said that it was not yet appropriate to label the killings as either hate crimes or serial murders.

Several hundred people attended a vigil for the victims at the mosque on Tuesday evening. Muslim leaders, as well as Roman Catholic, Jewish, Sikh and Mennonite residents spoke about the losses absorbed by Albuquerque’s Muslim community.

“The last two weeks have been nothing but nightmares,” said Tahir Gauba, a director of the mosque. Referring to the arrest of the suspect, he added, “Tonight the Muslim community will sleep in peace.”

The police in Albuquerque first disclosed last Thursday that three killings between November and August could be linked. The next day, a fourth Muslim man who worked as a truck driver was shot and killed in his car, raising further alarms in a city where many refugees and immigrants said they had long felt safe.

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Mr. Syed had immigrated from Afghanistan and lived in Albuquerque for five or six years, Commander Hartsock said. He said Mr. Syed had faced several domestic violence charges in recent years that were later dismissed.

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The report that the killings might be linked to a sectarian dispute raised the specter of the kind of violence that many immigrants from conflict-ridden countries had hoped to leave behind.

Sunni and Shiite Muslims differ in their beliefs over who was the proper successor to the Prophet Muhammad when he died nearly 1,400 years ago, a foundational dispute that today drives rivalries over religion, territory and political power. The conflict has fueled sectarian violence in several countries, including Iraq, Lebanon and Afghanistan, but it has been rare in the United States.

Muslim groups quickly condemned the killings and any hint of conflict in the U.S. Islamic community.

“Like Protestants and Catholics, the Sunni and Shia communities in this country live near each other, work with each other and marry each other in peace,” said Edward Ahmed Mitchell, the deputy director of the Council on American-Islamic Relations, a civil rights group. “There is no significant history of violence at all in the U.S. between Shias and Sunnis.”

For years, the authorities in Albuquerque had sought to shape the city into a haven for immigrants. Hundreds of refugees from Afghanistan have settled in the city over the past year, since the withdrawal of the U.S. military in that country.

The latest killings come as Albuquerque has been upended by a harrowing spike in gun violence, with the city on pace to see more murders this year than any other on record.

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Scrambling to respond, the Albuquerque Police Department began bolstering patrols around the businesses and places of worship that serve as gathering places for the city’s Muslims, estimated to number from 5,000 to 10,000 in a city of over half a million.

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Yet with the recent killings, many Muslims said they had begun to feel like targets, and fear was even driving some people to make plans to leave New Mexico.

Indeed, the killings jolted an increasingly diverse city, where immigration, largely from Mexico and other Latin American countries, is a major source of population growth and integral to the city’s history. Immigrants from the Middle East, including Muslims and Christians from Lebanon and Syria, put down stakes in Albuquerque and other parts of New Mexico in the late 19th century.

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