They are a very general feeder and will consume a great variety of stored foods, seeds, pet food, spices, and pastry mixes. This beetle lays eggs in almost any dry, organic substance. The eggs hatch into a small, white grub, which causes most of the feeding damage in the stored product. At maturity, the grub pupates and in a short time the adult emerges. The entire life cycle from egg to adult takes about two months at room temperature. When the adults emerge, they disperse to find new sites to infest. This dispersal phase is what you found on your window sill.
Check all organic materials in the room where the beetles were found and discard the infested products. If the infested product is something you wish to save, place it in a plastic bag and put it in the freezer for 72 hours. If it is a large object, it will have to be fumigated.
The room where the infestation occurred should be thoroughly cleaned. Vacuum all drawers, cupboards, cracks and crevices to remove insects and food debris. Place uncontaminated food items in glass or metal containers, or other insect-tight containers. Remember, however, that drugstore beetles will chew through plastic ware to get out. Spray the cupboard or drawer where the infestation occurred with a “food safe” insecticide to kill insects that may have escaped your cleaning process.