A 15-year-old girl was brutally beaten and kicked in the head by a gang of other teenagers on a Seattle bus platform while several security guards stood by and watched.
In the chilling surveillance video that caught the assault on tape, the victim is seen being jumped from behind by another girl in front of three uniformed security guards.
As the victim falls to the curb of the Westlake Center transit terminal, she is straddled by the assailant and then surrounded by other teens who start robbing her of her belongings.
One security guard can be seen standing directly over the victim as she is kicked in the head.
Despite the apparent brutality of the attack, the girl suffered only minor injuries like scrapes and bruises, as well as the loss of hair from it being pulled out.
The incident is under investigation by both the King County Sheriff's Office and the Metro Transit Police, sheriff's office spokesman Sgt. John Urquhart said.
"Transit tunnel security officers were on the platform and witnessed the assault," said Urquhart in a statement. "However they did not intercede as they are unarmed, civilian employees."
Urquhart told ABCNews.com that the security guards are trained not to become involved in violent confrontations or fights but are instead told to call 9-1-1, which they did.
Asked whether he believed it was a problem that the security guards weren't able to intervene, Urquhart responded, "That's an issue Metro Transit is looking at."
In a statement given to The Associated Press, Metro Transit's general manager said it is revising its policy that guards only "observe and report" problems.
Calling the attack "egregious," Urquhart said that the transit terminal where the attack occurred has a reputation for being quite safe.
Girl Beaten by Teens as Security Guards Watch
"This is an anomaly this doesn't happen very often," he said.
The altercation broke out at approximately 7:15 p.m. on Jan. 28, inside a Macy's and then later a Nordstrom's department store in the Westlake Center, a mall in downtown Seattle.
When an 18-year-old male member of the group got "in the face" of the 15-year-old victim and threatened to kill her, the group was asked to leave the store and the victim was followed outside, where she was assaulted, Urquhart said.
During the assault, some of the assailants stole the victim's purse, book bag, cell phone and iPod, according to police.
Four people ranging in age from 15 to 18 have so far been arrested and the King County Sheriff's Office is still looking for a 17-year-old male who was allegedly also involved in the attack.
One of the alleged assailants, a 15-year-old female, has been charged with second degree assault, a felony in Washington, and the remaining suspects are expected to be charged with robbery later today, according Urquhart said.