SAN BERNARDINO, Calif. » At a church, a mosque, a makeshift street-corner memorial and other sites, they gathered Sunday to mourn the 14 victims of the San Bernardino massacre and lament that the community has now been added to the tragic list of U.S. cities scarred by terrible violence.

Residents struggled to come to terms with the violence and hoped the community would unite in mourning and not be divided by the disclosure that the killers were a religious Muslim couple.

“It’s unfortunate that we’re on this list now, a list like Newtown, Aurora and others where such tragic events occurred,” Rep. Pete Aguilar, D-Calif., told a crowd at a mosque. “It’s not how I want San Bernardino remembered.”

In the wake of the attack, President Barack Obama delivered a prime-time address, telling the nation the attack was an “act of terrorism designed to kill innocent people.” While there was no evidence the shooters were directed by a terror network overseas or were part of a broader plot, “the two of them had gone down the dark path of radicalization,” he said.

Investigators were looking into what led Tashfeen Malik and Syed Farook to attack the gathering of Farook’s co-workers on Wednesday. Authorities were trying to determine if Malik, who was born in Pakistan and spent considerable time in Saudi Arabia, radicalized her American-born husband, Farook, and was the driving force behind the rampage, two officials said Sunday.

That possibility emerged late last week when it was disclosed that Malik had pledged allegiance to the Islamic State group in a Facebook post about the time of the bloodbath at a holiday luncheon. Malik, 29, and Farook, 28, were killed in a furious shootout with police hours after the attack.

Obama said Sunday, “We cannot turn against one another,” but he also said radicalism has spread into some Muslim communities and has become a problem that Muslim leaders “must confront without excuse.”

On Sunday, scores of mourners, including members of the Muslim community, visited a growing memorial on a corner near the social service center where the shooting took place. There were American flags, a poster that read “Pray for the world,” balloons, candles and cards. Many said they hoped the community would pull together.

“I’m trying to use it as a teaching thing for myself and for my children that horrible things happen, but it doesn’t mean that everybody is a horrible person,” said Eric Abrams, of San Bernardino.

At the St. Catherine of Siena Catholic Church, where shooting victim Yvette Velasco worshipped, the service focused on the need to get beyond the anger. Many parishioners said they would reach deep into their faith to find some way to forgive.

More than 100 people gathered for an interfaith memorial service at a mosque where Farook had occasionally prayed. Silver-framed photos of the victims were placed on a table at the Islamic Community Center of Redlands, with a candle lit for each.

Muslim community members said they are feeling both grief over the loss and fear of a backlash against their community. They encouraged community members to come together and not live in fear.

“It is really sad that we meet because of this. It is sad that only in death are we able to celebrate humanity,” 30-year-old mosque member Ajarat Bada said, fighting back tears.

Many in the crowd wrote personal notes to the victims’ families that the mosque will deliver.

Federal investigators continued trying to establish what pushed the couple to carry out what appears to be the deadliest attack on American soil by Islamic extremists since 9/11.

“I think I can’t say definitively right now what led either of these two to pick up guns and become murderers. I consider that is the focus of our investigation,” Attorney General Loretta Lynch said on NBC’s “Meet the Press.”

“We’re looking at everything we can find out about these two killers’ lives — how they grew up, where they grew up, how they met. All of those things will provide us guidance.”

One U.S. official said there appears to be nothing in Farook’s history that would implicate him as the driver of the attack.

Separately, a law enforcement official said investigators are looking into whether Malik was radicalized in the Middle East, where she spent considerable time, and used her 2014 marriage to Farook to penetrate the U.S. and commit jihad. But the official said it is only one among a number of theories that are being pursued.

The two officials were not authorized to discuss the investigation publicly and spoke on condition of anonymity.

While radical Islamic groups at times have mobilized women as suicide bombers, and extremist women may exhort their men to attacks, it is extremely rare in conservative Muslim societies for female jihadists to take part in actual combat, as Malik did.

Former college classmates of Malik’s and others who knew her in Pakistan said that in recent years, she began dressing more conservatively — including wearing a black head-to-toe garment or a scarf that covered nearly her entire face — and became more fervent in her faith.

Tami Abdollah reported from Washington. Contributing to this report were Associated Press writers Zarar Khan in Islamabad, Pakistan; Asim Tanveer in Karor Lal Esan, Pakistan; Aya Batrawy in Riyadh, Saudi Arabia; and Amy Taxin in San Bernardino.