The Massapequa High School senior was at a local bagel shop Tuesday when he made the threats, investigators said, according to CBS New York.
According to the District Court felony complaint, Bernhardt told a fellow student, "I hate everyone and I hope I get the chance to kill everyone." The complaint also states Bernhardt said, "I want to blow up the school," "I want to go to Europe and kill people," and "I have a list of people and wish they were in the Colorado Dark Knight shooting."
According to the complaint, the second student became fearful and said she believed Bernhardt would act on the statements, so she immediately went to the school and notified personnel of the threats, CBS New York reported.
School staffers then identified Bernhardt and the teen was later arrested at his home, police said. They said he had no weapons in his possession and that no weapons were found in his home.
Nassau County police charged him with making a terrorist threat, which is a felony. The teen appeared in court Wednesday where he pleaded not guilty. Bail was set at $30,000.
Bernhardt's father, Bob Bernhardt, said it was another student who made the comments.
"His story was that, I'm going to speculate a little bit, the kid came up to him and said 'hey, how's it going -- great to be back at school' and my son said 'I hate this place' and allegedly this John said then 'why don't you blow it up' and my son's response was like 'I am too much of a pansy, I would never do something like that,'" he said.
In a letter posted on the school's website, Massapequa High School principal Dr. Barbara Williams said, "Every threat is taken very seriously and any student or students who are guilty of such an action will be subject to the maximum penalties found in the Code of Conduct."
Some students who know Bernhardt said arresting him may have been too harsh.
"I wouldn't have exactly arrested him," one girl said. "I would have probably gotten him help more than getting him arrested or putting him in jail."
"People do joke around like that," said another student.
"They went a little bit far with it," another student said. "If the kid was actually serious - I don't think he was - but if he was serious, then they did the right thing."
Bernhardt's lawyer said the teen has been bullied in school.