ON SUNDAY, AUGUST 5, as Sarbpreet Singh was driving home from Baltimore with his family, his daughter’s iPhone began picking up reports of a mass shooting at a Sikh gurdwara, or temple, outside Milwaukee. A flurry of phone calls and news reports soon confirmed the tragedy: A man linked to white supremacist groups had killed six people and wounded three.

The shooting rocked the Boston-area Sikh community, which has gurdwaras in Milford, Millis, Everett, and Medford. But it presented an opportunity to educate people about the monotheistic faith, which has about 20 million members worldwide, mostly in India, and emphasizes egalitarianism, sharing, and service. So Singh, a longtime leader in the Milford gurdwara , worked with Christian, Jewish, and Muslim leaders to organize a late-August service rooted in Sikh tradition, along with a customary communal Sikh meal, at Trinity Church in Copley Square. “At some level, all of us understand that there are things that are common between various faiths,” says Singh, a 49-year-old from Hopkinton who runs a technology start-up. “And yet it’s so easy to focus on our differences.” Singh says he and other local Sikhs were surprised when as many as 1,500 packed into Trinity to show solidarity. Participants lingered afterward to eat, talk, and mourn. “It was surreal,” he says.