(CNN) -- She had come alone to the Richmond High School homecoming dance, gorgeous in a sparkling purple dress and faux diamond baubles. The DJ played salsa, meringue, rap. When the teenager disappeared, her friends thought she had gone home early.
Except she never said goodbye.
"We were going to go look for her," said Kami Baker, 16, a junior at the school.
The next day, Baker learned the ugly truth about what had happened to her friend.
According to police, she had been gang raped and beaten for almost 2½ hours and left unconscious under a bench shortly before midnight Saturday night.
"I busted up crying," Baker said.
The campus incident in the Bay Area city north of Oakland has shaken students and their families. Baker was one of many people connected to the school and the community who lashed out at officials at a public safety hearing Wednesday.
Baker blamed school district officials for not doing enough to protect her school -- and her friend. She said none of the four officers who were at the homecoming dance was patrolling the school premises even though there were a dozen young men hanging out just a few feet from the gym entrance. She says school officials chose not to take any action.
"I looked outside of the gym and I saw 12 to 15 guys, sitting there, with no IDs," Baker said at the hearing. "The officers -- not only did they not check the IDs of those students or men sitting outside of of our campus, but the security officers who are employed here did no ... checking either. The assistant principal looked outside and actually saw those men, and did nothing about it."
Baker took the podium with her younger sister, Barbie, a freshman at the school, who had spent a chunk of Saturday evening with the rape victim.
"This story has disrupted the school's morale greatly, including my own. I am friends with the girl," Baker said. "When I started here, I felt extremely unsafe and so did she, due to the lack of police officers and security officers."
Baker later described the 15-year-old girl as a churchgoer who struggled to fit in at Richmond High.
Four teenagers were arraigned Thursday on charges connected to the incident. Cody Ray Smith, described by the court as over 14 years old, pleaded not guilty to charges of rape with a foreign object and rape by force.
Two other juveniles, Ari Abdallah Morales and Marcelles James Peter, appeared together with Smith at the Contra Costa County Superior Court, but did not enter a plea. The court described Morales as under 16, and did not give an age for Peter.
All three juveniles, who wore bulletproof vests at the hearing, were charged as adults. A fourth individual, Manuel Ortega, 19, appeared separately without an attorney and did not enter a plea. He did not wear a protective vest. Another adult who was arrested has a different court date.
As many as 10 people were involved in the assault in a dimly lit back alley at the school, police have said. Another 10 people watched, without calling 911, police said.
The victim was released from a hospital Wednesday, police said.