Common sense suggests that they could be armed themselves and had more in mind to do if they got away with the shed.
'Great, we've got all the power tools, shall we leg it or shall we go into the house and knife the homeowner? yea lets do that' ?
Where do we draw the line where we act upon people on our land/property without permission?
The problem is of course that simply being on your land without your permission is not a criminal offence....