Ty is someone's brother. Someone's ex. Someone's classmate. Someone's killer. 
 From the moment the student body finds itself locked inside the auditorium while Tyler stares them down with a gun, the book doesn't let up. The story rotates through several points of view--the ex-girlfriend, the sister, the sister's girlfriend, the girlfriend's brother--each of whom has a unique perspective on the situation, unique fears and concerns. There are heroes, would-be heroes, survivors, victims. I don't agree with every character's choices--I think a couple of them could have saved themselves--but I understand their motivations. 
 I couldn't make much sense of the blog posts and tweets interspersed in the narrative. I understand the outside perspectives, but they didn't add much to the story. 
 ARC provided by NetGalley.