The cabal wants to kill people to send a message to Trump that he is a dead man, like Kennedy. But they know that if they shot up ANOTHER Parkland High School, that would be too obvious and the public would figure it out. So they send the message by shooting up a different TEXAS high school and dumping a box of ammo on PARKLAND. That way POTUS gets the message, and they capture the media narrative which is always their secondary goal.
Now remember, they HAVE TO TELL TRUMP that he is in the bullseye. They have to explicitly communicate that the CABAL WILL ASSASINATE DONALD J. TRUMP. They have to do this because Satan will only give them credit for the murder if they warn Trump first. If they failed to do this, they would not get the brownie points but instead would be punished with the usual KARMA for murdering somebody. This is part of a satanist process to escape the karma and still do the evil.