Nikolas Cruz was hooked on weapons and violence ... and that obsession was played out over and over again on his social media pages.
The 19-year-old posed with guns, knives and even bragged about killing a frog on his Instagram account. Cruz is also seen sporting a Donald Trump's "Make America Great Again" hat in another post ... and Cruz allegedly posted pics of shotguns and military-grade rifle bullets on another personal Instagram account.
As we reported ... Cruz participated in at least one training exercise with a white supremacist group.
Cruz -- who 9 months ago threatened to carry out a mass shooting -- is accused of using an AR-15 rifle to carry out the murders. He remained silent while his charges -- 17 counts of premeditated murder -- were read aloud Thursday in court.