The latest news is that law enforcement is seeking search warrants for Cho's e-mail & cell phone records, reportedly to obtain information about his relationship with the first female victim. How is such a warrant reasonably calculated to uncover evidence of a prosecutable crime? Both the shooter and the victim are deceased.
Unless they have developed specific information that someone else may be criminally culpable, this is nothing but a fishing trip and, if they were to trip over evidence that someone else may be criminally culpable, it would likely be thrown out of court for lack of probable cause for issuance of the warrant, jeopardizing any future prosecutions.
Curiosity is not a sufficent basis for issuance of a search warrant. I agree that the information they seek may be important, but this is not the way to go about it. If I were a magistrate, I would deny the warrants unless they had specific, articulable information to support them that someone else may bear criminal responsibility and the information sought is reasonably anticipated to disclose evidence thereof.