Authorities insist a theory that a Muslim angry over Internet postings was responsible for the slaying of an Egyptian Christian family is just one of several under investigation.

But the theory — embraced as fact by some — has touched off a new round of anti-Muslim sentiment in a city still stinging from a post-Sept. 11 backlash.

Grief and rage erupted Monday at the funeral for the slain family members, who were found bound and fatally stabbed in their home early Friday. Mourners fought in the street, with many blaming Muslims for the deaths.

As the coffins were carried through the streets to St. George & St. Shenouda Coptic Orthodox Church, one protester's sign, above a photograph of the smiling Armanious family read: "American Family Beheaded on American Soil. Welcome Bin Laden." Others declared: "Terrorists Reached Our Home" and "Bush: Crush Sleeper Cells."

Church official Amil Sarofiem begged for order.

"Get out! We don't need any talk about Sept. 11 or Muslims!" he yelled to a man who was shouting anti-Muslim slogans.

Investigators are looking into the possibility that Hossam Armanious (search), 47, his 37-year-old wife, Amal Garas, and their daughters, Sylvia, 15, and Monica, 8, were slain by someone angered over postings that Armanious, a Coptic Christian, wrote in an Internet chat room. The Coptic Orthodox Church (search) is one of the oldest communities in Christendom, believed to have been founded in the first century A.D. by the apostle Mark.

Authorities say the killings could have occurred during a robbery since no cash or valuables were found in the home. Prosecutor Guy Gregory said the father's wallet was found empty.

The Armanious family had been active in the church since immigrating to the United States in 1997 from Egypt, where Copts generally live in peace with Muslims.

The 2,000 mourners included about two dozen Muslims who took off their shoes as a sign of respect and placed them near the entrance to the church, just as they do in their mosques.

"We feel this is something that was very far away from our community," Ahmed Sheded, president of the Islamic Center of Jersey City (search), said after the service. "A real Muslim can't do that."