BOSTON (Reuters) - An Arizona man was sentenced to 15 months in prison on Wednesday after admitting he made online threats to bomb Harvard University and shoot students at its first commencement ceremony for black students in order to “end their pro-black agenda.”

Nicholas Zuckerman, 25, wept as he apologized to a federal judge in Boston for the “hateful” threats he posted on Instagram in May 2017 at a time when he was regularly being “amped up” reading about politics.

Prosecutors said he made the online comments in response to news reports that the Cambridge, Massachusetts-based Ivy League school would hold a special commencement ceremony on May 23, 2017, to celebrate the accomplishments of black graduates.

“If the blacks only ceremony happens, then I encourage violence and death at it. I’m thinking two automatics with extendo clips,” Zuckerman wrote in an Instagram post 10 days before the ceremony, according to prosecutors.

That same day, prosecutors said, Zuckerman under the username “russian_goalkeeper94” posted another online comment, which read: “#bombharvard and end their pro-black agenda.”

“As defendant himself recognized, this was a serious offence,” U.S. District Judge Indira Talwani, who imposed the sentence, said. “People going to attend a celebration instead had to worry.”

The ceremony went forward as planned with a heightened law enforcement presence. The FBI eventually tracked Zuckerman down in Arizona, and in an interview he admitted making the threats, prosecutors said.

They said Zuckerman, who is white, picked his victims specifically because they were black.

Cara McNamara, his attorney, in court said that Zuckerman had a history of mental illness. She sought to frame his threats in a broader context, saying he was “operating in an environment where people every day are pushing the limits.”

“In my heart, I have no hate,” Zuckerman said in court. “I’m truly sorry. I want to get out and stabilize and be a good member of society.”

Zuckerman was arrested in June 2018 and pleaded guilty in February to two counts of transmitting a threat to injure another person. He is expected to receive credit for year-plus in custody he has already served.

In addition to the prison term, Zuckerman was sentenced by Talwani to serve three years of supervised release, the first six months of which will be in a halfway house.