Seitz told KPIX-TV that she was going to talk about how she was allegedly sexually assaulted by another student - who was in the audience at the ceremony - and the school's lack of response.
"I thought this is a public school with freedom of speech", she told the newspaper.
Seitz planned to bring up her account of a student that assaulted her last fall, she told ABC News. "She had the opportunity to display her message to all of us, but we were there just to celebrate leaving and she's taking it off into what happened to her", Nick Mall, another graduate of Petaluma High School.
It was then the microphone audio is cut.More news: Robert De Niro apologizes to Canadians for Donald Trump’s behaviour
However, the school's attempt to silenceSeitz voice did not help. 'It wasn't an easy thing to do to go up there and say what I said or tried to say'. Chants of "let her speak" could be heard from fellow graduates following the silence.
Seitz told NBC's Bay Area outlet that her attacker was not given any consequences for his alleged actions, and he was in attendance at graduation.
According to the outlet, administrators had approved Seitz's graduation speech but cut the mic when she veered away from it. "This is for my class that stood up and said 'let her speak.' Even if the administration doesn't give me a mic, I still want to speak". "Sometimes we know what's right and have to do it despite the threats".
"This is what they've been doing", she said of the school. She spoke about classmates persevering through the devastating wildfires in Northern California that destroyed some of their homes, and what it was like being in school during teacher strikes. "We have all at some point been hurt, excluded or - worst of all - ignored".More news: Rickie Fowler Engaged to Allison Stoke
"In Lulabel's case, her approved speech didn't include any reference to an assault", he said.
"Just based on the patterns of where my speech was going - I was just saying some people, it was very vague". The video has been viewed more than 28,000 times. "I realized that this is a big injustice and needs to be spoken about".
She said the incident was reported to police and the student, whom she didn't name, was arrested.
But Seitz wasn't done speaking.
She ended up returning to her seat, and later posted her full speech online, including the part that was cut off: "Even learning on a campus on which some people defend perpetrators of sexual assault and silence their victims, we didn't let that drag us down".More news: Trump pulls out of joint G7 statement, calls Trudeau 'weak'