By Jericka Duncan

PHILADELPHIA (CBS) – For the last 15 years, 37-year-old Joseph Keller has been answering to mailman.

These days his co-workers, including his supervisor and twin brother Mike, have another name for Keller, hero.

“I’m not a hero,” proclaimed Keller, “just a guy at the right place at the right time.”

Last month, while delivering mail in Brookhaven, Keller noticed something strange; a three-year-old walking alone Beechwood Street.

“I got six beautiful children at home,” said Keller. “When I saw her I couldn’t help but to help her.”

He spent nearly an hour with the toddler, asking residents if they knew her, before calling police.

“About 15 minutes later I noticed a group of people looking, Keller explained.”I called the police station and they brought the little girl back.”

His “right timing theory” has happened before. In 2008, Keller says he successfully performed CPR on a colleague who was having a heart attack at work. He also helped one of his customers get a new bike, after it was stolen.

His postmaster says his keen sense of awareness to what’s going on around him led authorities to a bicycle theft ring.

“He’s just excellent with people, excellent with customers,” said Chester Postmaster Maureen McKenna.