The recent beheadings of two American businessmen in the Middle East may have added to anger against Arab-Americans and Muslims that began after the 2001 terrorist attacks.

The murders of Paul Johnson (search) and Nicholas Berg (search) triggered hate mail, verbal attacks and anti-Muslim signs. Muslims received death threats and their mosques were vandalized.

"Since 9/11, every time there is an incident overseas attributed to Muslims or Arabs, we go on orange alert ourselves," said immigration lawyer Sohail Mohammed (search). "There are individuals here who are off the wall, who think that every woman who wears a hijab or every man named Mohammed is out to blow things up."

Al Qaeda-linked militants in Saudi Arabia decapitated Johnson, an American engineer, after warning that they would kill him if the Saudi government did not release jailed comrades. Berg met a similar fate last month in Iraq.

Following Johnson's death, anti-Islam signs surfaced around the rural New Jersey neighborhood where he once lived. One read "Stamp Out Islam" next to a drawing of a boot over a crescent and star. Another, hung on a mailbox next door to Johnson's sister's home, was more detailed.

"Last night I wasn't a racist, but today I feel racism towards Islamic beliefs," it read. "Last night Islamics had a chance to speak up for Paul Johnson, but today it's too late. Islamics better wake up and start thinking about tomorrow."

The New Jersey attorney general sent bias crimes investigators to the area, along with stepped-up state police patrols. The signs are gone now, replaced with hand-lettered placards on utility poles that say "Our prayers are with the Johnson family."

But more anti-Muslim graffiti appeared Thursday on a Muslim man's home in Egg Harbor Township.

"It's really our fear coming true," said Faiza Ali of the New Jersey chapter of the Council on American-Islamic Relations (search). "It indicates a hatred that could turn into something violent."

The day after Johnson's death, a coalition of Muslim groups held a rally to condemn the killing in Paterson, the heart of New Jersey's Arab-American community.

A few days later, vandals tossed empty liquor and beer bottles at a mosque in Union City as congregants inside mourned a teenager who died in a car crash.

"If they are throwing empty bottles today, they could be throwing rocks, or worse, shooting at us tomorrow," said Aref Assaf, president of the American Arab Anti-Discrimination Committee's (search) New Jersey chapter.

Two mosques in Florida were vandalized in the days after Johnson's killing. In the Tampa suburb of Lutz, someone broke into the Islamic Community Center and scrawled "Kill All Muslims" on the mosque's interior walls, then smashed windows. In Charlotte Harbor, someone vandalized a mosque's sign and left threatening phone messages.

In the St. Louis suburb of Ballwin, Mo., vandals painted a swastika and the word "Die" on the wall of the Dar-Ul-Islam mosque.

In Texas, dead fish were dumped near the entrance sign to a mosque under construction in a suburb of Houston.

And in the Chicago suburb of Orland Park, residents urged officials this past week to reject a mosque's building application. A Baptist pastor told a public hearing he feared it would attract Islamic extremists and violence. The center was approved over boos and catcalls from the audience.

"I believe the time is coming when Muslims will not be safe inside the U.S. borders," one man wrote to CAIR. "I see nothing wrong with us doing the same things to them that they are doing to innocent people."

"It is high time you people wake up and smell the blood," another man wrote to Assaf's group in New Jersey. "Turn in the terrorists. They are your relatives, in a lot of cases. Cousin Omar. Uncle Mohammad. You know what I mean. Until you come forward to help us stamp out this vermin, you are as bad as they."