Their arrival basically destroyed Native Americans--their lives, their communities, their cultures--everything.
They were enslaved, forced into labor, and horribly mistreated. The Europeans brought with them diseases that the Native Americans were not immune to, so many of them died from diseases like smallpox and measles. In Amherst, Mass., a man named Jeffrey Amherst actually gave the Native Americans blankets infected with disease (I believe it was smallpox) to kill them off.
The Native Americans were protecting their land, so of course they attacked the Europeans. The Europeans, upon learning that the land was not theirs to just take, embarked on a massive killing spree. The Native Americans were 'in their way.' The Native Americans were murdered and raped, their villages destroyed.