Richmond High School students walk past a sign during gym class before a rally and vigil concerning the gang rape of a 15-year-old girl outside of Richmond High School's homecoming dance in Richmond, Calif., Tuesday, Nov. 3, 2009. (THE ASSOCIATED PRESS/Jeff Chiu

RICHMOND, Calif. - Officials at a high school where a student was gang-raped in a courtyard are moving to tighten campus security with the long-stalled purchase of surveillance cameras, powerful lighting and new fencing.

The measures were disclosed as community leaders sought ways to calm outrage over the Oct. 24 attack at Richmond High School that police said may have involved as many as 10 suspects and 20 onlookers who failed to call police.

"Obviously, there wasn't enough security or we wouldn't have had this tragedy happen," said Bruce Harter, superintendent of the West Contra Costa School District.

Administrators have long pushed for the new measures but couldn't find the money until now, Harter said.

A seventh suspect was arrested Tuesday in the attack on the 15-year-old girl after she left a homecoming dance in the industrial enclave near the San Francisco Bay known as one of the nation's most dangerous cities.

At a rally and candlelight vigil later Tuesday, DeAnna Schlau with the non-profit Community Violence Solutions read a statement she said was prepared by the victim.

"Violence is a wrong choice. We realize people are angry about this, but let that anger cause change; change that is necessary to keep our children, our neighbours and our friends safe. We thank everyone for their love, support and ongoing prayers," Schlau said.

Hundreds attended the event, which featured songs, prayer and dancing.

Ten chaperones, six site supervisors and four police officers were at the school gym to make sure the dance and nearby parking lots were safe. They thought things were going so well that two supervisors were allowed to leave early, Harter said.

The girl was attacked across campus, where a group of males ranging from 15 to the mid-20s were drinking in the dimly lit courtyard. The victim was invited by a classmate to join the group after leaving the dance.

She drank a large amount of alcohol with them before the two-hour assault began, police said. Officers acting on a tip later found her semiconscious near a picnic table.

Charles Johnson, a Richmond High School security specialist, said one of the supervisors at the dance had been keeping an eye on the girl as she waited outside the gym for her father to give her a ride home.

Sammie Lee Hill, a former police officer and a community relations specialist at the school, said the victim is a caring person and easy to get along with.

"We all know she's going through a hell of an ordeal," Hill said. "That's what hurts everybody the most."

Earlier Tuesday, police arrested Elvis Josue Torrentes, 21, for investigation of rape, rape in concert with force and other allegations that could lead to life in prison if he is convicted. He was being held on $1.2 million bail.

Prosecutors have filed charges against five other suspects.

Janet Gutierrez, 16, a junior at the school, said the rape has made her concerned about her own safety.

"I'm not scared to be in school," Gutierrez said. "But I'm not going to walk around outside, especially when it's dark."

Community leaders were asking for 100 volunteers to help keep the school safe.

"I pray that we can use this horrific and heinous incident as a teachable moment," said the Rev. Andre Shumake, who made the plea.