BOSTON (CBS) – Investigators have released excerpts from the diary of the man who allegedly gunned down Air Force veteran Ramona Cooper and retired Massachusetts State Trooper David Green in Winthrop last month.

Suffolk County District Attorney Rachael Rollins said Nathan Allen “carried hate fueled by white supremacy.”

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State Police recovered many journals from Allen’s apartment. According to investigators, he wrote, “White people are the worlds apex predators” and “they know they are inferior to us.”

Nathan Allen. (Image Credit: Suffolk District Attorney)

Police say the 28-year-old was carrying two handguns when he stole a truck and allegedly shot the two Black Winthrop residents on June 26. Allen was shot and killed by Winthrop Police.

Allen was researching white supremacy online and wrote racist notes in his journal up until 48 hours before the murders.

In a notebook called “The Allen Diaries” he wrote “Racism is healthy and natural. And holding it in is bad for you.”

“To see it in his own handwriting, in multiple notebooks it just left nothing to the imagination and made very clear what this individual’s intent was that day,” Rollins said.

Winthrop Police Chief Terence Delehanty emphasized the writings don’t represent the town. “These are disgusting despicable comments,” Delehanty said. “He didn’t go to school here and he didn’t grow up here.”

State Police continue to examine Allen’s past and are seeking to speak with anyone who came into contact with him prior to the shootings.

In his last passage before the crime, Allen allegedly wrote about trying to get his wife on board with his beliefs, but investigators say his family has been completely cooperative and never saw this coming.

“It’s really, really scary. The level of vitriol and the level of hatred,” said Robert Trestan of the Anti-Defamation League.

Trestan says there are questions that still need to be answered.

“Who inspired him? Who are the people that he was talking to? What are the other publications and books that he studied and at what point did he become radicalized?” Trestan said. “He didn’t just write things. He made a decision that I am going to go out and kill people.”

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Investigators are also looking into the possibility Allen was headed for a local synagogue with the stolen truck when he accidentally crashed into the home. Staff