It came down to this: a cavalcade of police cars, a chorus of cheers, and then – a man in white, waving to the crowds.

Pope Francis passed through Philadelphia on Saturday night. He came through like a strong wind, impossible to ignore.

For tens of thousands of faithful who had waited all day, his brief appearance was worth the hours spent on hard curbs.

Among the throng: Father Josh Allen and his flock of pilgrims from Georgia Tech. They boarded a bus in Atlanta Thursday at 11 p.m. to head north. Fifteen hours later, they were in Philadelphia.

Saturday morning, Allen and his aspiring engineers staked out a spot on the parkway, hoping Pope Francis would pass them on his way to the nearby Festival of Families, scheduled for Saturday night.

Saturday evening, those moments of waiting had dwindled. Allen put on a Georgia Tech cap and grinned. It provided a bright contrast to his black cassock.

“Hey, I’m a Tech grad.” He’s class of ’99, with a degree in management.

A graduate of seminary studies, too. The illness and death of his mother, Allen said, prompted him to take a hard look at his priorities. He gave up a budding career in an equity firm after her death in 2006. Five years later, he was a priest.

His journey to priesthood, he said, was a long one. “I was an atheist,” he said.

After study, prayer and talking to others, “I came to the realization: The Catholics had it right.”

He gestured at a clutch of students, most wearing T-shirts that proclaimed, “Helluva Catholic, Helluva Engineer.”

The only dark part of the day: Tech’s football loss to Duke. The Catholics fell to a university with Methodist roots.

“I can’t say anything about that,” he said, “without using bad words.”

Davis Aasen struggled to find the right words to describe the defeat, and gave up. It was easier, said the Peachtree City resident, to focus on the pope. He craned his neck to look toward City Hall, an ornate building rising in the distance. Crowds stretched in all directions.

“His love for Christ is genuine,” said Aasen, a senior in biomedical engineering. “That love is really apparent.”

Aasen said his faith weakened – until he enrolled at Tech. There, he became active in the Catholic Center, and felt his belief renewed.

He’s considering medical school – a career as a surgeon would be nice – but he also feels a more ecclesiastical tug.

“Maybe,” he said, “God wants me to be a missionary.”

Translation: a priest.

His girlfriend, Ana Gomez, hopes God has other plans for him. She met Aasen more than a year ago. Like him, she’s studying biomedical engineering. A ballet dancer, she’s fascinated with the mysteries of motor control, that link between mind and muscle.

A native of Fort Lauderdale, Fla., she was raised to be a good Catholic. It was, she thinks, a one-dimensional upbringing.

“My understanding of being a Catholic was, ‘You should be a good girl and God will reward you if you keep your nose out of trouble,’” she said. As she grew, Gomez said, she came to understand her faith more fully.

Francis has helped that understanding, she said.

“He shows us that sanctity is not esoteric or unachievable,” she said. “Everyone is called to be a saint. The humility and love that he shows means it’s possible.”

The pope is the right leader at the right time, said Elizabeth Waters, of Houston. She’s 21, a senior in mechanical engineering. Maybe, one day, she’ll be an automotive engineer.

“If I saw the pope?” she asked. “The first thing I’d tell him is thank you for agreeing to become a priest … and becoming a leader for all of us.”

Waters, her smile as bright as the September sun, nodded at her classmates.

“I think one of the reasons we’re excited is not just seeing the pope, but to experience it in a fellowship like this,” she said. “That’s why we have such a big presence.”

“We can’t wait to see him,” she said.

That wait ended at 7:17 p. m. when Francis passed by. He appeared luminous in the street lights. He waved, and everyone waved back. The crowd let out a roar the angels must have heard.

He came by a second time, on the other side of the parkway. Again, people screamed, cameras flashed, and the pope waved.

Waters stood back and smiled. Fifteen hours on a bus, 11 on the parkway, for 30 seconds. Time well spent, she said, of the pope appearance moments before the start of the global Festival of Families, which was expected to draw hundreds of thousands.

“It was pretty cool – pretty surreal, actually,” she said.

Allen smiled, too. “Every time you see him,” Allen said, “your heart just leaps.”