#4. Tommaso Ciampa
Tommaso Ciampa defeated Aleister Black a few weeks ago on NXT to become NXT Champion for the first time in his career.
Ciampa only defeated Black because of interference from Johnny Gargano, and could easily be in the mindset that he knows he won't retain his title in a triple threat match, and therefore he needs to get rid of one of his challengers.
Ciampa is smart, so he knows that the odds are stacked against him at Takeover: Brooklyn since he wouldn't have had to be pinned to lose his title. Despite how smart he is, Ciampa was still spotted at Full Sail University in the parking lot minutes after the attack so it appears that Ciampa is one of the biggest suspects in the case right now.