Rabia Chaudry kept her 7-year-old daughter home from her private Islamic school in Maryland on Thursday, fearing anti-Muslim backlash from Wednesday’s massacre nearly 3,000 miles away in San Bernardino, Calif.

“I think we are all feeling exhausted and very vulnerable,” said Chaudry, a lawyer and national security fellow at the New America Foundation. “I’m angry at those people who did this attack. And I’m angry at how this is being politicized. Everything boils down to, ‘We should fear Muslims. And they shouldn’t be here.’ ”

American Muslims say they are living through an intensely painful moment and feel growing anti-Muslim sentiment after the recent Islamic State attacks in Paris and this week’s San Bernardino shootings, carried out by a Muslim husband and wife.

The motivations of the California killers are still unclear, although authorities are investigating it as a potential act of terrorism. Muslims said they are bracing for an even more toxic climate in which Americans are increasingly suspicious of Muslims.

Muslims say that Americans, like many in Europe, often do not draw a distinction between radical Islamist militants, such as those associated with the Islamic State and al-Qaeda, and the religion of Islam and its followers who have no ties to extremism.

Thursday’s New York Post reported the San Bernardino massacre story with the headline “MUSLIM KILLERS.”

Arsalan Iftikhar, a human rights lawyer who is working on a book on Islamophobia in the United States, said that headline was evidence of how people jump to conclusions about a suspect in a crime who is Muslim.

“When a Muslim American commits a murder, their religion is brought front and center,” he said. “With anyone else, [it’s] a crazy, kooky loner.”

Many Muslims said fear of Islam is being fueled by the heated rhetoric of Republican presidential candidates, particularly businessman Donald Trump, who has called for surveillance of some mosques and requiring Muslims to register with the government.

That may be smart electoral politics: A 2014 survey by the Pew Research Center showed that 82 percent of Republicans said they were “very concerned” about the rise of Islamic extremism in the world, compared with 51 percent of Democrats.

“Islamophobia is the accepted form of racism in America,” Iftikhar said. “Leaders like Donald Trump show us that you can take a potshot at Muslims and get away with it.”

Estimates of the number of American Muslims vary from about 4 million to perhaps 12 million.

Assistant director in charge of the FBI's Los Angeles field office said it was "way too early to speculate on motive" for the San Bernardino attacks. (Video: Reuters)

The backlash against them has created a deepening sense of alienation. Talk of creating Muslim databases and noting Muslims’ religion on their IDs has echoes for many of the forced internment of Japanese Americans during World War II. Many mosques have asked local police for more security.

“There’s a constant climate of insinuation of terrorism and disloyalty that creates this pervasive sense of being an outsider,” said Haroon Moghul, a fellow at the Institute for Social Policy and Understanding in Washington.

On Tuesday morning, Terry Cormier arrived to open her Anaheim, Calif., Islamic clothing shop and found a Koran, riddled with more than 30 bullet holes, left at the door. She made a report to police and the Council on American-Islamic Relations (CAIR), whose officials called it “a note that says, ‘You’re not welcome here.’ ”

“Our Koran is something that is very important to us and that we hold very dear, and to see it full of bullet holes and defaced and intentionally delivered to me to find is a hate-filled message,” said Cormier, a California native who married an Egyptian immigrant and converted to Islam. “Whoever did it, I think they probably didn’t have any understanding of the religion itself.”

Cormier, who wears the head scarf known as the hijab, said she has felt little anti-Muslim sentiment in her ethnically diverse community in Southern California until now.

“But especially after what happened yesterday in San Bernardino, it’s pretty intense,” she said. “But I really think that if people would just get out there and talk to a Muslim person, they would see that they are human just like you. We’re just as upset about what’s going on and how people are being hurt. It’s devastating to us as well.”

Pew studies show that since the 9/11 attacks, Americans have become far more likely to think that Islam encourages violence more than other religions might. A Pew survey in March 2002 found that 25 percent of Americans held that view, and the number reached 50 percent by September 2014.

Research by Pew and CAIR shows that apprehension about Islam has increased sharply with the rise of the Islamic State, also known as ISIS and ISIL, in the past two years, especially since the group’s highly publicized beheadings of foreign journalists and aid workers began in August 2014.

“After 2010, we had a few years where things seemed to be getting better,” said Corey Saylor, national legislative director at CAIR. But he said the beheadings “set us back down a darker path. . . . People of goodwill are trying to do work to bring people together, and it just takes a few moments of ISIS’s time to unravel all of that.”

Anti-Muslim violence in the United States has jumped since the Paris attacks, including gunfire and vandalism targeting mosques and assaults against individual Muslims.

One recent evening, Haneen Jasim, 22, a University of Cincinnati pre-med student who wears the hijab, said she had just left a Starbucks where she was studying for an exam when a man approaching in a car began honking his horn.

With his window rolled down, he began shouting insults at her and called her a terrorist.

“He was yelling, ‘Paris!’ and told me to go back to my country,” Jasim said in an interview.

As he yelled, she said, he drove toward her, “almost running me over.” Three people pulled her to safety on the sidewalk, she said.

“I’ve never gotten anything negative about being a Muslim, ever,” she said. “I always read articles about other people, but I honestly did not think it would happen to me.”

Jasim said the encounter has bolstered her resolve to educate others that her religion is not about violence, that Islamic State militants are not true Muslims. She said she would organize an anti-Islamophobia rally Friday on campus.

But the incident has also left her scared, for herself and her three younger sisters.

“I am terrified. My friends are scared. My family is scared. I’m scared for other people, but this is an opportunity to show to people what Islam is, instead of what the media or ISIS shows.”

At least one Muslim was also wounded in the San Bernardino attack. Khaled Zeidan, board chairman at the Islamic Community Center of Redlands, said a Muslim woman was shot in the legs and is in stable condition.

“We’re all grieving. We’re all together in this,” Zeidan said. “We’re all hurting, whether people want to believe it or not.”

Muslim leaders are also debating whether they need to apologize each time Islamic extremists carry out an attack, said Adem Carroll, a member of the Muslim American Civil Liberties Coalition in New York.

“If our voice is not included, that silence is interpreted as acquiescence or guilt,” Carroll said. “We’ve been in a position since 9/11 where we have to prove our innocence, which is the opposite of the way it should be.”

Other Muslims think that moderate Muslims need to be more aggressive about denouncing acts of terror and rejecting the Islamic State’s call to establish a caliphate — a Muslim homeland ruled by sharia.

On Friday at the National Press Club in Washington, a group of American Muslims will announce the Muslim Reform Movement, calling on other American Muslims to reject the caliphate and advocate for the equality of men and women.

"We need to deal honestly with issues of extremism," said Asra Nomani, an author and activist who is part of the group. "As long as Americans see denial and deflection, it feeds distrust."

Muslims, Nomani says, need to directly address how extremist Muslims interpret the Koran and how that affects church-state relations.

"What we're struggling with is on the far right, a lot of people who want to deal with Islam in a monolithic way, and on the far left, no one wants to acknowledge there's a larger problem," Nomani said. "The truth lies somewhere in the middle. There is an extremism problem. The majority of Muslims don't live that way, and we have to reclaim a middle path."

At Dar Al-Hijrah Islamic Center, a Falls Church mosque that was targeted by a man throwing smoke bombs and a Molotov cocktail on Nov. 19, leaders said they would respond to the current “culture of intolerance” by touting good works done by Muslims at the mosque.

Imam Johari Abdul-Malik said he was pointing out his community’s outreach efforts, including a weekly food pantry serving 250 families, mostly non-Muslims; free Thanksgiving dinners for the needy; and an upcoming countywide coat and blanket drive for displaced persons in Syria.

“The best defense is offense,” Abdul-Malik said. “People are telling other people to be afraid of what you do? Then let them come and see what you do.”

Julie Zauzmer and Alice Crites contributed to this report.