"You can't walk in there with a certain demeanor or you'll get it right back," McDonald said. "But you can't walk in there as a pushover or you'll get that right back, too."

He also knows this: He loves being a police officer. McDonald realizes that might sound "corny," as the kids put it. But he grew up in a factory neighborhood where he always assumed work would be a sentence, not a joy, that "any job meant you punch in, and then you're miserable."

McDonald was freed from that, years ago, on the day he was hired to work as a police dispatcher.

"It was an important role, and there was a sense you were helping to make a difference," McDonald said.

It inspired him to become a court officer, then to attend the police academy and to seek a full-time job on the beat, a dream that became real for him four years ago.

At night, he goes home to his wife, Danielle, and their two young kids, a son and a daughter who are about the same age as he was when he lost his brother and his dad. The pain of everything that was taken away is now balanced by the joy and depth of everything he's earned.

Yet every day, as he deals with city children at high risk, he is conscious of his own journey – and how easily it could have gone another way.