By Greg Argos

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CHESTER, Pa. (CBS) — Police arrested a man accused of feeding crystal meth to his stepson in Chester County. The man and his wife were arrested after police say they left the children inside a truck in a Walmart parking lot in Parkesburg — engine running, with a gun and ammo.

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It was the day before Christmas when police conducted a traffic stop at the Walmart.

District Attorney Tom Hogan says, by sheer coincidence, that officers on the DUI stop noticed a Chevy pickup with the engine running around 3:40 a.m..

So he walked over, peeked inside and noticed three children and a handgun on the center console.

“This car has been out there running for an hour,” Hogan said. “The parents then show up.”

“The gun, I have no idea what they were thinking.”

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Both were arrested.

Harold Nuse, the children’s stepfather, and his wife, Brandy, were charged with endangering the welfare of the three children — boys ages 11, 8 and 6.

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“Some time goes by, we have the kids in a safe place,” Hogan said.

Weeks passed and Hogan said investigators finally built a rapport with the three brothers and were able to question them with the help of child abuse interviewers.

It turns out, one of the boys made a startling admission.

“One of the little boys tells us he was being fed crystal meth by his stepfather,” Hogan said. “He was taking him out to his shed and telling him, ‘You do this.’ At one point, the boy spit it out and he made him put it back in.”

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“And this happened at least five times,” Hogan noted.

Now, Nuse and his wife are still in jail and being held on $75,000 bond.

Their truck sits empty in front of their Honeybrook home.

“This is great work by the state police,” Hogan said. “They’re doing their job on the one side with the DUI stop and they have the presence of mind to see what else is going on.”

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“They rescued these three boys,” he said. “If it wasn’t for them, these boys could have been killed by that gun or killed by the ongoing administration of crystal meth.”