Unnatural Causes (2008)

Matt and Julia aren't having the greatest relationship on earth. They've got a successful advertising agency but Matt suspects his wife of having an affair and is getting so obsessed with this thought that he's actually asked his co-worker Trevor Jones to have her followed. Trevor, who wants to become partner in the company, does as requested and when he brings pictures to Matt that show Julia talking with another man, Matt goes berserk and wants Julia dead. When word of Julia's death little later spreads, Matt gets remorse and kills himself. But Julia isn't dead and it seems that Matt's suicide might actually have been a murder...