The computer forensics take a long time. Remember he smashed up his hard drive.
IF there was a conspiracy or some internet idjit that encouraged this kid in his destructive delusions they need to be held to account.
Let's give LEO the time and space to make sure.
Why would Lanza smash his hard drive? He was on a murder/suicide mission, whatever was found on his hard drive would be totally irrelevant. However, if others were involved in the shooting, they would want to destroy evidence.