Monica Cannon-Grant, who is organizing Thursday’s rally on the Town Common for Mikayla Miller, questioned why the individuals who had a confrontation with the Hopkinton teenager prior to her death have not been charged and said that she wants Middlesex District Attorney Marian Ryan to “step down and let the FBI handle this case.”

Appearing on WGBH’s “Greater Boston” show Tuesday night, Cannon-Grant voiced her frustration with how the investigation has been handled.

“Everything about this case has been a lack of transparency and it insinuates that something is being hidden or covered up,” she said. “And for those reasons we are demanding an independent investigation and it be taken out of DA Ryan’s office. Because we cannot trust in the fact that we’re going to get all the answers necessary to [determine] what happened to Mikayla Miller.”

Ryan also appeared on the program (just before joining the Hopkinton Select Board for its emergency meeting) and defended her office’s work. She has insisted that no conclusions have been made in the case, and noted that until results are released from the medical examiner, a determination on the cause of death will not be made. Ryan added that “there is absolutely nothing unusual” about the long wait for information.

Host Jim Braude and Cannon-Grant pressed Ryan about the altercation on April 17, when four teenagers confronted Miller in the clubhouse of her apartment complex, apparently after a relationship between Miller and one of the females had ended. Miller’s mother called police later that day, and her daughter detailed the incident, Ryan said.

“What we know is that there was a physical assault that Mikayla described,” Ryan said, adding: “Mikayla reported to the police that she had been punched and shoved.”

Questioned about the race of the individuals, Ryan said, “My understanding is that those individuals, some were white and some were Latinx.”

Asked if she thought a crime had been committed by the teens, Ryan said: “Yes, based on what we know, yes.”

Cannon-Grant said if the teens — two of whom are males — were Black instead of Miller, the response from authorities would have been much different.

“I feel like her office has mishandled this case thus far, to acknowledge that blood was on Mikayla when the police interviewed her, a report was taken, she stated she was jumped, she gave names, they talked to the individuals, they looked at the [security] camera. If I was jumped by four people … and I have blood on me and made a report, there would be an arrest,” Cannon-Grant said. “There needs to be an arrest. She acknowledged a crime was committed, still no one has been arrested. This is unprecedented, it does not happen. If the roles were reversed, these people would be arrested.

“The other thing is this, Mikayla was found tied to a tree, standing on her feet with a belt wrapped around her neck. Mikayla had on a black sweatsuit that does not require a belt. Everything about this case says that something is being hidden, and it does not feel good. And for those reasons we want an independent investigation with the FBI, and we’re going to do an independent autopsy.”

Ryan’s office said early on, “This is not a suspicious death investigation and there is no foul play.” Cannon-Grant and the family, however, claim Miller was murdered.

“In regards to it being a murder, it’s because the same day these individuals jumped Mikayla, at around 7 in the evening, after her mom had called and reported that something had happened, a few hours later, Mikayla leaves the house, her location was shared via Snapchat with these same individuals, and she ends up dead,” Cannon-Grant said. “Now, the frustration is this: If Mikayla was a white child and this was five black children that had engaged in this activity, not only would they have been charged for an assault, but they would have had their faces all over social media, the media and everywhere else.”