Perhaps this remark has already been responded to, but, consider that fact that he's an electrician and consider the fact that bombs need to be wired by someone who... knows how to wire things. Ergo, perhaps he was in the building doing some 'electrical wiring' work...
speculation, to be sure- but might it be possible he not only was helping in the wiring of bombs, but was indeed acting as a test of security.
The fact that he's illegal... wouldn't surprise me if he was doing work on the low down.
I like the way you think.
Very possible scenario.