"Bottle bombs" or "Drano bombs" are currently occurring more often than usual in Baltimore (as well as some other places). This type of "prank" has been around for a while anyway, but it's become a bit too "popular" to ignore.
Kids are putting Drano, tin foil, and a little bit of water (often colored to look like left over cola) in plastic drink bottles and capping it up - leaving it on lawns, mail boxes, in gardens, driveways, etc..
If the bottle is picked up, and shaken even just a little bit, the combination takes about 30 seconds to build up enough gas which then explodes with enough force to remove fingers, eyes, etc. The liquid is also boiling hot and not so very good for the skin.
Be careful picking up any plastic bottles you see lying around the yard, gutter etc.