Video obscured for first few seconds.The Metro Transit Police continue to investigate the beating of a 15-year-old girl late last month in the transit tunnel at Westlake Center.Three security guards saw the Jan. 28 assault, part of which was filmed by surveillance cameras. But the guards aren't armed and are trained not to get involved in physical confrontations, according to the King County Sheriff's Office, which operates Metro Transit Police.Still, the incident has prompted King County Executive Dow Constantine to order a review of Metro security."Public safety is our top priority. I am appalled by the sight of uniformed guards standing by while a person was kicked and beaten," Constantine said. "I have ordered a full review of all operating polices that govern Metro's contract with civilian security guards to determine what changes must be made. People have an expectation of safety when riding public transit, and we must take every measure we can to assure that."In the days since the assault, at least four suspects have been arrested.The assault followed incidents at both Macy's and Nordstrom, where a group of 10 to 12 teenagers and young adults created a disturbance, the statement said.At one point, an 18-year-old man confronted the 15-year-old girl and threatened to kill her.The group was told to leave Nordstorm, the Sheriff's Office reported. The group then likely followed the girl to the tunnel.Another 15-year-old girl who was with the large group began assaulting the victim on the station platform.The victim was shoved into the right of way, but no buses or trains were nearby. She was also knocked to the ground and kicked in the head.In addition to being beaten, she was robbed; her purse, book bag, cellphone and iPod were stolen.Security officers saw the assault, but didn't stop it.The Sheriff's Office gave this explanation for the guards' inaction:"They did not intercede as they are unarmed, civilian employees of Olympic Security Services. They are trained to not become involved in violent confrontations or fights, but are directed to call 9-1-1, which they did via the tunnel communications center."In addition, they were significantly outnumbered by the group."But Metro Transit intends to change what guards can do, including the direction to "observe and report" but not get involved in fights."You look at what's happening to the victim and you say something's got to be changed," Metro Transit General Manager Kevin Desmond told KING-TV/5. "That's just not going to be acceptable. We've had that 'observe and report' for years in our contract and this incident clearly shows that we need to change that."The suspects had fled by the time Seattle police officers responded.The 15-year-old girl who delivered the beating was arrested over the weekend and was booked into juvenile detention, according to the Sherrif's Office statement.Detectives also arrested two men, ages 18 and 20, and an 18-year-old woman on Saturday. According to the Sheriff's Office statement, the three were involved in the assault, robbery or threats to kill the girl. One of them may also have acted as a lookout.A 17-year-old male suspect is still at large.Scott Sunde can be reached at 206-488-8331 or scottsunde@seattlepi.comSoundoff (99 comments, Hide/show comments)