Mr. Rocha suddenly found himself braving a Quebec winter, jobless, isolated and unable to speak French. After an initially rocky adjustment, he proposed to Sonia at a teahouse, hiding a $150 ring in a teacup. He said he found a sense of purpose after Sonia’s aunt, who worked in the Shaar’s kitchen, helped get him the janitor job.

He felt immediately at home at the synagogue, he said, and was particularly drawn by the spiritual meaning of a bar or bat mitzvah, the rite of passage in which a boy or girl affirms a commitment to Judaism. He would sometimes pause from vacuuming to sit in the pews and listen, entranced, to Cantor Zelermyer’s haunting voice singing prayers.

“I am a baptized Catholic, but in a synagogue I feel a very strong connection, something talks to me,” he said.

It was while dusting the pews and observing bar mitzvah photographers at work that the idea first entered his head that photographing bar mitzvahs was his “destiny.”

“I would see the photographers standing too close to the bar mitzvah boy, and the voice in my head would be saying: ‘No, no, no, it’s all wrong. You have God giving you this light, and you aren’t doing anything with it,’” he recalled. “But I was the janitor, so I kept dusting.”

Then came the bris epiphany.

The grandmother was so delighted with the resulting moody, cinematic photos that she paid him $130 for the job, an improvement on his $10-an-hour janitor salary.

Emboldened, Mr. Rocha asked the synagogue’s management if he could shoot other events. Within two years, he was photographing weddings and bar mitzvahs, for as much as $8,000, and, for a while, changing afterward into his janitor’s uniform to scrub toilets. Sometimes he worked such long days he slept on a synagogue pew.