With an American flag and thank-you card, Long Island veteran Billy Richards is offering police officers across the country a mix of empathy and support.

Richards, 34, a personal trainer from Islip and former Army sergeant, started by jogging around police stations in Suffolk County.

“I can relate a little bit to what they do,” he said. “As a veteran, I’ve been a defender overseas. The police are a defender on the homefront.”

Now he has taken his mission on the road.

Since July 29, he’s visited a number of cities where officers have recently died or been wounded in the line of duty, including Baltimore, Dallas and Baton Rouge, Louisiana. On Saturday, he stopped in San Diego to honor two officers shot there.

“It was a last-minute decision there,” he said. “I got the command watch officer and handed him the card.”

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Richards, who left the military in 2012, said he intends to visit a few more cities before returning to Long Island in a few days.

He completes a 3- to 5-mile run at each police station before presenting a flag and card. Funding for the trip was provided by friends, family and supporters through a GoFundMe page on the internet.

While few of the stops have been set up more than 24 hours in advance, Richards said he has received a warm welcome at each.

A visit to Hattiesburg, Mississippi, on Tuesday generated local news coverage after Richards dedicated his run to two officers killed there in May 2015.

“It’s an honor to be recognized by somebody who, No. 1, does not live here,” said police spokesman Lt. Jon Traxler.

The next day, in Dallas, police escorted Richards to the site where five officers were killed by a sniper on July 7, said Cpl. Debra Webb, a department spokeswoman.

Richards chronicles each visit with photographs and a video that he posts on Facebook and Instagram. Visit www.facebook.com/billyamania/.