Do not leave spades and other tools in sheds as they are commonly used by those of dubious nature to lever open locked doors on other buildings. Over the years I have been to many burglaries where the offender entered the garden shed,removed tools and used them to break into the house.
Secure your shed and don't leave anything of value (radio, tv, mobile phone) visible and you remove the motive of the offender.
I would fit a shed alarm made from a personal attack device rigged to the door with fishing wire. You can get them from your local crime prevention officer (council or police) and they work like a grenade (no they don't blow burglars to bits!!!!) you pull the pin out and they scream out at 130 Decibels frightening the living dung out of the naughty person.
I designed the kits for several residents in my area and they worked so well that they are now produced for other areas.
Gardenplot, the world is 90% good and honest but there are some horrible nasty people out there, mix them with a combination of drink and drugs and you will get what you witnessed. I work for the police and was on nights last night when a group of 10 local chavs beat the living daylights out of a 20 year old innocent bystander for no reason other than pure fun. They followed him into an alleyway near a local nightclub and all jumped him, putting him in hospital. Thankfully there was a good witness and three were arrested the youngest being 14.
There is little deterrent in todays society for criminals , no punishment for crime and little reward or encouragement in life for "doing the right thing."
Society is due a big correction and one day decency and values will be held high again. My grandfather recently told me "it will take a war to rebuild this country," I think he is right!!!!!!