A school therapist warned that Parkland school shooter Nikolas Cruz had “dreams of killing others” while “covered in blood” roughly four years before his 2018 rampage at Marjory Stoneman Douglas High School, according to a letter presented at his sentencing trial Thursday.

Rona O’Connor, a staffer at Cross Creek School, reached out to Cruz’s psychiatrist Dr. Brett Negin to sound the alarm about the disturbing admission, adding that Cruz was prone to “extreme” mood swings, according to the note.

Negin was shown a copy of the June 2014 letter by Cruz’s defense attorney while on the stand Thursday — but testified that he had never received it.

Roughly four years later, Cruz rampaged through the Parkland, Florida, school with an AR-15 rifle, killing 14 students and three staffers.

O’Connor’s letter said that Cruz was routinely “verbally aggressive in the classroom” and “is usually very irritable and reactive.”

“At home, he continues to be aggressive and destructive with minimal provocation,” the letter states. “For instance, he destroyed a television after losing a video game he was playing.”

Cruz also used a hatchet to chop away at a dead tree near his home and used knives to destroy furniture, according to the note.

“He has a preoccupation with guns and the military and perseverates on this topic inappropriately,” according to the letter.

Cruz, 23, has already pleaded guilty to committing one of the worst mass shootings in American history.

Jurors will now decide if he gets the death penalty or a life term.

Cruz’s defense attorneys argue that his traumatic and dysfunctional birth and upbringing warrant the lesser sentence.

Prosecutors contend that the enormity of the crime calls for Cruz’s execution.