When Rabbi Gavriel Noach Holtzberg and his wife left New York for India to run a Jewish outreach center, the Israeli-born couple worked tirelessly, serving homemade kosher meals to their many guests and strengthening their connection with God.

Their outpost was in Mumbai, a dusty and chaotic port city. But the pair never let the tough conditions prevent them from creating a comfortable home for Jews visiting India or from helping the needy.

"They were amazing people," said Hillary Lewin, 24, of New York, who met the Holtzbergs last summer at the center in India. "They had this wisdom, courage and braveness about them. It's a shame. The world needs people like them."

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The 29-year-old rabbi and his 28-year-old wife were killed this week after gunmen assailed the ultra-Orthodox Chabad-Lubavitch movement's center in Mumbai, one in a series of attacks across India's financial capital that left six Americans dead.

The couple's toddler son, Moshe, was rescued by an employee and taken to his grandparents. At least eight people died at the Jewish center.

Three other victims in the building apparently had been visiting there, said Rabbi Zalman Shmotkin, a spokesman for the organization, whose world headquarters are in Brooklyn.

He said the dead included Bentzion Chroman, an Israeli with dual U.S. citizenship; Rabbi Leibish Teitlebaum, an American from New York City; and an Israeli woman whose name was not released. An Israeli official told FOX News that a sixth American citizen was also killed at the Chabad center, but the State Department could not confirm any details.

Other Americans killed in the attacks were a man and his teenage daughter from a Virginia community that promotes a form of meditation, a colleague said Friday. Alan Scherr, 58, and daughter Naomi, 13, died in a cafe Wednesday night, said Bobbie Garvey, a spokeswoman for the Synchronicity Foundation.

The U.S. State Department confirmed that six Americans were killed in the attacks but offered no details.

Mayor Michael Bloomberg said the deaths of the three victims from New York were "tragic losses" for the city. He said Teitlebaum, a Brooklyn native who moved to Jerusalem several years ago, was a kosher food supervisor.

Holtzberg was born in Israel and moved to Brooklyn with his parents when he was 9. He had dual U.S.-Israeli citizenship. The Israeli Foreign Ministry said Rivkah Holtzberg had only Israeli citizenship.

"Gabi and Rivky Holtzberg made the ultimate sacrifice," said Rabbi Moshe Kotlarsky, vice chairman of the educational arm of Chabad-Lubavitch.

The Holtzbergs arrived in Mumbai in 2003 to run a synagogue, provide religious instruction and help people dealing with drug addiction and poverty, Kotlarsky said.

He said Holtzberg's last known call was to the Israeli consulate. Holtzberg said that "the situation is not good" before the phone went dead, according to Kotlarsky.

Twelve hours after gunmen stormed the center Wednesday, Sandra Samuel, a cook at the center, heard little Moshe's cries outside the room in which she had barricaded herself. She opened the door, grabbed the toddler and ran outside with another center worker. The little boy's pants were soaked with blood, and Samuel said she saw four people lying on the floor as she fled.

Members of the Chabad-Lubavitch movement gathered at the group's headquarters Friday to pray for the families of the dead.

The Scherrs were among 25 foundation participants in a spiritual program in Mumbai. Four others on the mission were injured in the cafe attack in the luxury Oberoi hotel, including two women from Tennessee, Garvey said.

"I would call them bright stars," she said of the Scherrs. "Extraordinary, bright, very positive — examples to the world."

Scherr was a former college professor who lived at the Synchronicity sanctuary near Charlottesville, Virginia. His wife and her two sons did not travel with them to India.

According to the foundation's Web site, the community is led by Master Charles, a former leading disciple of Swami Paramahansa Muktananda. He is described as "one of the most popular spiritual teachers from India to build a following in the West in the 1970s." He taught a form of yoga.

Garvey identified the Synchronicity injured as Helen Connolly of Toronto, who was grazed by a bullet; Rudrani Devi and Linda Ragsdale, both of Nashville, who underwent surgery for bullet wounds; and Michael Rudder of Montreal, who remains in intensive care after being shot three times. Other members of the mission narrowly escaped the attack.