NEW YORK - By the time congregants of the Riverdale Jewish Center arrived for morning services Thursday, the police were gone and the reporters had begun to show up. Nearly 12 hours after four men were arrested in connection with a plot to blow up the synagogue - as well as the Riverdale Temple and a military air base - neighbors gathered outside the house of worship with a mixture of curiosity, anxiety, fear and gratitude toward police for thwarting the attack. "We are shocked," said David Winter, the executive director of the Riverdale Jewish Center, who was at the synagogue Wednesday night for a meeting with other clergy. "We have close ties to Israel, there's always a sense of what's possible, but we're still shocked, followed by relieved." Josh Loberfeld, who lives two blocks away from the RJC in Riverdale, said around 9 p.m. he heard sirens outside his apartment building. When he looked out the window, he said, "I saw there were a fleet of cop cars racing up the block." He was shaken when he turned on the news and learned about the foiled plot. Within hours, the synagogue e-mailed congregants to assure them that the area was safe. "Obviously, it wasn't going to blow up, according to the FBI and the NYPD and Homeland Security. Just the thought that something like this can happen or could have happened makes me extremely nervous and paranoid. What else is out there?" Loberfeld said. Thursday, he sent his children to school as usual, but he described lingering feelings of unease. "How can this happen in our neighborhood?" he asked. Jewish organizations issued a flurry of statements, condemning the plot and praising law enforcement officers. "While tragedy thankfully was averted, this is a poignant reminder that homegrown terror in the United States remains a real possibility," said David Harris, the executive director of the American Jewish Committee, in a statement circulated by the group. Stemming potential backlash, the American-Arab Anti-Discrimination Committee also publicized a statement from its leaders that called the bomb plot appalling. "This alleged act of hate is absolutely unacceptable," said the group's national executive director, Kareem Shora. "ADC has been consistent in condemning hate-motivated crimes and any attacks aimed at civilians." Meanwhile, Wednesday afternoon, Muslim and Jewish leaders convened a joint prayer service at the Islamic Cultural Center of New York, known as the Great Mosque. Led by Imam Muhammad Shamsi Ali and Rabbi Marc Schneier, president of the Foundation of Ethnic Understanding, the leaders condemned the planned attacks. "We are against hate," said Schneier. "It is reassuring, for me, to hear the voices of prominent leaders speaking out by condemning these planned acts of terrorism and violence." But elected officials said the plot underscored the threat of homegrown terrorism. "We have to be extremely vigilant," Rep. Peter King of New York, the senior Republican on the House Homeland Security Committee, told CNN's Anderson Cooper on Wednesday night. Thursday morning, Assemblyman Jeffrey Dinowitz, a Democrat who represents parts of the Bronx and lives near the RJC, said, "Fortunately, no one was hurt. No one was killed." The assemblyman added: "I'm angry, I'm scared, that people would be trying to do [this] because we're Jews."