New Baltimore, Mich. ? A drugstore sales receipt for duct tape led police to two suspects in a double-killing and the discovery of a third body in the pickup truck they had been driving, authorities said Wednesday.

The receipt had been left at the New Baltimore home of Scott Berels and his pregnant wife, whose bodies were discovered last week.

Scott Berels, 27, had been beaten and both he and Melissa Berels had been suffocated in what appeared to be a robbery and murder, New Baltimore Police Chief John J. Bolgar said Wednesday.

Police traced the duct tape receipt to a local CVS store, which had video surveillance. Bolgar said a tip from someone who saw the video led them to Samantha Jean Bachynski, 19, now charged in the killings.

Bachynski and her fiance, Patrick Alan Selepak, a 27-year-old on parole after serving 10 years for armed robbery, were arrested Tuesday in a motel parking lot in Owosso. In the pickup they were driving, police discovered the third body, believed to be the truck’s owner.

Genesee County Undersheriff James Gage would not say how the victim was killed but confirmed that the body was wrapped in plastic similar to the New Baltimore victims.