That...sounds like an interesting legend. And an interesting way to become a national hero, too.
Even better than that, it was actually two legends for the price of one! The bishop he chopped also became legendary - a saint.
The details of the story vary depending on from which side the story it's told, of course. It's agreed that Saint Henry was traveling Finland converting the heathens when one day he came to Lalli's house. Lalli wasn't home, so the group paid his wife for food and hay for their horses and then went on their way. For some reason that's never explained the wife apparently lied to Lalli afterwards that the group had ransacked the house instead and he got so angry he followed the (for some reason already escaping) group until he finally caught up to the bishop and killed him with an axe. He took the bishop's hat and put it on his own head, but as he came home and tried to take the hat off his whole scalp fell off with it.
The other way of reading the story is that the house indeed was ransacked, or that the wife of Lalli had no option but to comply with the uninvited guests' demands and received no pay. This all happened in midwinter... a group of men suddenly emptying the food storage meant hunger and possible death to Lalli's whole family.
It's an interesting legend on its own, and the best part is that it's most likely entirely made up. There was no need for anyone to convert Finland at this time since the country, especially the area Saint Henry was said to be in, had already been Christian for almost 200 years and the historical records around him don't quite match the legend either. There's
more about Saint Henry here and
Lalli here.