BUT, LE knew that this had a "graphic" message...not typical of a "drug deal gone bad" and they knew that two other people had been in the apartment just prior to the murders. They also knew that the murders occurred on Sept 11th and that there was no sign of forced entry. None of the neighbors heard any noises that might have suggested a violent struggle took place. (Suggesting that the turned over furniture was an afterthought, IMO.)
LE knew plenty to start an in depth investigation on BM's so-called best friend who was a no show at the first vigil/ceremony, the funeral and the one year anniversary memorial. Even the gym owner saw that TT abruptly stopped coming to the gym to workout.
LE had plenty of reason to at least check on the welfare of the so-called best friend and finding him alive and well to question him for info that might help in the investigation. By the time of the murders, Russia had already alerted the US govt about their concerns re: TT and his mother.
And in Ariel Castro's case, LE knew his daughter was the one to last see the victim before victim went missing. Still they never interviewed Castro. Just because LE might have plenty of reasons to do something, doesn't mean they will do it.
Furthermore, FBI never told to LE anything about Russia warning them about TT.
And, furthermore, FBI didn't have a clue as to who TT was, since they had to release his photos to the public. I really fail to see why they would be asking public for help if they were following TT.