The charges that have been filed are pretty general. As you suspect, they may arise from Guy Heinze Jr. trying to conceal some sort of involvement with drugs. However, he may just be a user who was trying to get rid of drugs and paraphernalia that could cause him trouble during the investigation. He still could be innocent of the murders.
Obviously, the critically injured person, assuming they recover enough to be interviewed, is going to be key in understanding what happened.
Good thoughts. However, I saw earlier on Fox that the only survivor is 3 years old. He/she probably won’t be too much help, unfortunately.