Derek Graham encountered the woman and child on Tuesday evening.
Graham, a senior trooper in West Virginia, and another trooper had stopped a female driver who was was "highly intoxicated," Graham told The Washington Post in a phone interview Friday.
The troopers started taking inventory of the vehicle, and in the woman's back seat was a baby boy, Graham said. The child wasn't wearing pants or a shirt - just a diaper. And, Graham said, he was covered in vomit.
"I mean, he had vomit all over him, just covered from head to toe, vomit," Graham said. "You could smell feces, urine. It was probably the most disgusting thing I've seen thus far in my law enforcement career involving a child, especially an infant. "
The woman was placed under arrest, Graham said.
The baby headed off to the state police barracks.
Troopers brought him into the office - probably not the most child-friendly place, if we're being honest. The baby was upset and crying, Graham said.
"And just in my head, I'm a father myself, and I couldn't sit there and let him ... I couldn't let him sit in that," he said.
So Graham found a sink in a kitchen and gave the child a warm bath.
"It was actually really cool," Graham said. "He was crying, just so upset. And as soon as I got him there, and got some bubbles in there with him, we both locked eyes and it was, he started smiling, (at) which I started smiling. It was almost like he knew - he felt so much better. And he was just a completely different baby after that."
"He was the best little baby," another Trooper, B.R. Wood, told the Bluefield Daily Telegraph. "He had just started to nod off when CPS (Child Protective Services) arrived."
Graham said the state police contacted CPS "because we didn't even have a diaper, we didn't have anything." After the bath, Graham said, the boy was pretty wiped out. It had been a pretty stressful event, after all.
"He just laid on my chest," Graham said. "Like I said, we don't have pack-and-plays or cribs or anything. So he was my sidekick for the rest of the evening."
Troopers found the boy a teddy bear, Graham said, and he kept him close as he walked around the office.
"He was just clinging on to me for dear life," Graham said. "It was actually really special."
Graham said the baby had a "horrible croupy cough," and was in "bad shape." He is now in the care of a relative, Graham said, and the woman is facing criminal charges. She was so intoxicated during the stop she couldn't tell Graham the child's name, which he says he still does not know.
"I actually don't," Graham said. "It's really sad."
When he thinks about the incident now, Graham said, he remembers the smell, which he noticed before he realized the baby was covered in vomit. After he noticed that, something else kicked in, he said.
"It was almost just my dad instinct popped into play," Graham said. "Forget state trooper, forget law enforcement officer. It was dad that took over, said 'I gotta clean this little guy up.' "