SPOILERS! THEY'RE DEAD TOO!
When Patti and Samantha are in the kitchen, Samantha says she killed Stryker (and of course she killed Brooke too). She tells Patti, "Don't worry. I won't hurt any of your friends." Patti says, "It's only me." Sam says, "What do you mean." Patti says, "They're dead too." Sam says, "You? But why?" Then she screams as Patti stabs her to death.
Of the people murdered, Samantha killed Brooke and Stryker, and Patti killed everybody else. How did Patti know she was the only one left "it's only me" if she didn't kill Brooke herself? And if she saw that Brooke was murdered, wouldn't she be frightened that there was another killer out there and that she (Patti) could be killed next?
I read somewhere that when Stryker and Brooke fall out of the window, it's the snowmobile knocking them out the window (it was shown for a minute earlier in the film). The shots of Samantha shooting them were spliced in later. Since the scene of Patti and Samantha in the kitchen were among the last to be shot, they still could have fit that scene in with the continuity of the rest of the film.
Any comments, thoughts, feelings, whatever?
Patti, Brooke, somebody?