Orsaken till mordet

Very clever! 

Please walk now to the place marked with a golden star on the map!

It all started a long time ago when the person, the murderer (M), came out of the entrance of Västerlånggatan 42. When looking to the right M saw his wife kissing a man in the street crossing nearby. The fact that M knew who the man was made it even worse, it was the brother of his employer. M became upset and the feeling of disgust overflew him and M only thought about one thing – Revenge. The man went to the left on the street and the wife went to the right. M started to follow the man up to the left and did his best not to be discovered. During this sneaking, he got an idea of how to make them even. He had worked today at the dynamite factory and had some stuff in his pockets that could help out for a huge payback.

Title of the document What was the reason for the murder?