"I would ask you, as part of the sentencing, to grant me five minutes in a locked room with this demon," Margraves said, according to CNN. "Would you give me one minute?"
After Cunningham rejected his request, Margraves said, "Well, I'm going to have to," before launching himself at Nassar, CNN reported.
Crying could be heard in the courtroom as Nassar was escorted out. Assistant Attorney General Angela Povilaitis told families in the courtroom to "use your words," not violence.
"This is letting him have this power over us," she said. "We cannot behave like this. I understand this is a remarkable situation, but you cannot do this. This is not helping your children. This is not helping your community. This is not helping us."
After the incident, Cunningham told those gathered in court that she understood Margraves' anger, but she also cautioned against reacting with violence, the Lansing State Journal reported.
"If it is hard and difficult for me to hear what his daughters have to say, I can't image what it is like for a parent," Cunningham said, according to the Journal.
The incident occurred during the third and final sentencing hearing for Nassar on sexual abuse charges. The charges in this case focus on his work with Twistars, an elite Michigan gymnastics club. The hearing resumed after about 25 minutes.
During a similar hearing that ended last week, more than 150 girls and women came forward to say Nassar abused them under the guise of medical treatment.
More victims are expected to speak Friday. The proceedings are likely to extend into next week.
The Associated Press contributed to this report.