The WV Encyclopedia online has a better article on him, with some references.

It's not brought out in the articles, but the settlers should not have been there to defend. The end of the Seven Years' War did not allow more white settlements beyond the Alleghenies, but some tried it anyway. Much of what is now West Virginia was good hunting land , important during the winter months for the Seneca and other tribes, and settlers were not long tolerated. Wetzel and Wetzel's family were therefore attacked, when they settled in the vicinity of what's now Wheeling. After the Revolution seemed to open up the western territories, there was a a further complication when the tribes of the Northwest pointed out that they had not been included in the peace treaty, and their land was still not open to settlers. Wetzel murdered one of the Seneca chiefs involved in the negotiations with the new US government over this, which probably made the resulting Northwest Indian War even worse.

When Manifest Destiny was accepted and such settlers as Wetzel were considered pioneers, Wetzel was considered a hero. Now that we are able to see the colonization of the west and elimination of the Indians as not so beautiful , it's easier to see Wetzel for what he seems to have been, a very violent man who happened to be on the winning side.