You are a good Samaritan, indeed. But DO NOT pick up packages, book bags, backpacks or any other unidentified objects in a public place. This is how the Boston bombers delivered their mayhem, and it has become all too common practice. If you see an item left behind by someone, get away from it, and please notify authorities, but don't put yourself and others in danger by picking them up. Also, if you see a plastic bottle left anywhere, even your lawn, be aware that small bombs are being made by kids or whoever, and left around. All it takes is a few ingredients and a small ball of aluminum foil. They are motion activated and can go off if you pick them up.
http://www.snopes.com/crime/warnings/bottlebomb.asp Better to move it first with a long stick, or notify authorities. I know it sounds paranoid, but what happened last week can happen again.