WHATS' THe NAME OF MOVIE!?

this is seriously killing me! whats that movie that came out around 2005-2008 about this guy (teenager, sorta hot) whose leaving a party, and gets like almost murdered, and they're scared that they killed him so they threw his body in the sewer, and he's like dead but the only person that can hear him, is his killer, (female) and he's like leaving her hints on where to find him, but she's the ONLY one who can hear his voices. and there's like a huge search party looking for him. His mom in the movie is Siobhan Fallon. in the end, she finds him, and she gets like shot or stabbed and dies. so sad, but so good! the title is only like one word, but i just can remember. HELP!