Officer Nick Struck from Brighton, Colo. was on patrol last Thursday when he was dispatched to a fatal accident near Interstate-76 and Buckley.
Struck says: "so we started kind of attending to the kids."
The father died instantly. The mother and three of her four young children were injured. As paramedics worked to save them, they handed the fourth child, a 2-year-old girl, to Officer Struck.
"She was crying. She was actually soaked in gasoline from the truck, and so the smells - it was really awful," Struck remembers.
The way she fit into his arms reminded him of his own 2-year-old daughter.
"My daughter, who's the sweetest thing in the world, when she falls and cries she wants Twinkle Twinkle Little Star sung to her. So this girl, when I was out in the field, I was singing Twinkle Twinkle Little Star and pointing to the lights in the fire truck," Struck says.
Jessica Matrious, who saw the accident and stopped to help, took the picture.
"He was definitely trying to keep her from watching what was going on behind her," Matrious says. She says you could see the toddler relax as the officer softly sang to her.
"She put her arm around my shoulder just like my daughter does, and that's really when the emotions started kicking in," Struck says.
Matrious tweeted the picture, and it's been tweeted and retweeted thousands of times - literally posted now all over the world.
"It's humbling, for sure," Struck says. He says what he did is no different than what any other officer would do.
"It's kind of a little glimpse, but it really does happen all the time," he says.
The Brighton Police Department acknowledged Struck's actions on social media, posting, "We are extremely proud of the men and women of our department! Good work, Officer Struck!"
Brighton is about 25 miles northeast of Denver.