That kind of attentiveness defines Marren, who joined the force after retiring from Marine Corps, where worked law enforcement for 21 years, serving in Hawaii, Japan, Korea, and Washington, D.C.

“It’s very hard-core, and a lot of bases where I was stationed are as busy with the same kinds of incidents big cities deal with. That was a contrast coming to Harvard,” he said. “My personality isn’t hard-core. The chief used to say, ‘If you take care of the kids, everything else falls in line.’ Everything we do here at Harvard is about that young freshman coming in. We want the kids to flourish, be safe, and have a little fun.”

Deputy Denis Downing, Marren’s supervisor, called him “an ambassador of the University.”

“Just last week I watched Chuck get ready to go on patrol, and the last thing he did before he left was to polish his boots,” he said. “He comes to work every day with a smile on his face. He enjoys meeting and helping people and that is why he is successful. He is an officer whom I can always count on.”

For Marren, a typical day in the Yard or at Longwood doesn’t exist, and he is as skilled at storytelling as mugging for the camera. Many fall into the you-never-know-who-you’re-talking-to category. There was the early morning patrol of the Yard when a man in a floppy hat reading The Wall Street Journal on the steps of University Hall started chatting to him. He later realized it was T.H. Chan.

When former President George H.W. Bush received an honorary degree in 2014, Marren took his customary position, watching over the crowd from the stage at Commencement. Barbara Bush gestured insistently to him from her front-row seat in the audience.

“I walked over and asked, ‘Is everything OK?’ and she said, ‘I came a long way to see my husband get this degree. Can you get out of the way?’” Marren recalled.

There was the time Marren worked on a detail at Gund Hall. It was October 2014 and a woman came up and asked him where she could wait for her husband, who had gone to get their car. Marren made small talk as he walked her to the car, then saw the couple on their way. Five months later, he learned that his small gesture of kindness — along with some other positive interactions the couple had with HUPD — prompted the pair to donate $1 million to the force.

“In life you never know a person’s story, so be real. I try to treat people the way I want to be treated,” he said. “It’s also nice that HUPD gets recognized for all of the around-the-clock hard work that we do.”

Back in the Yard last week, Wang gave Marren a copy of the 2004 photo along with a CD of her debut album, “Sincerely.”

“In police work, you can go from the tranquility of the Yard to a life-and-death situation in a heartbeat,” said Marren, visibly moved. “We do everything.”