San Francisco police say there's been a series of violent robberies on Muni and bus stops in the

Visitacion Valley neighborhood since the end of July, five attacks in twelve days.

Police believe the suspects are a group of teens riding Muni, looking for victims.

Three of those suspects have been arrested but police say more may be involved in the robberies.

KTVU obtained exclusive access to surveillance videos from the most recent attack, which police have described as quick, vicious and heinous.

The video shows a petite Chinese woman sitting on the number 9 bus when one of the suspects walks up to her, grabs the woman and rags her off the bus. Police say that suspect is just 16-years-old.

The victim told KTVU she feared for her life.

"So scared, very scared," said the 39-year-old woman who asked to not be identified.

The woman told KTVU she was riding the bus home from work on August 6^th when the robber confronted her on the bus.

To make matters worse, the victim said there were many passengers on the bus who witnessed the attack and did nothing.

“I need help, but no helped,” she said.

She showed KTVU what’s left of the cuts and bruises she sustained in the attack. After the attack she received treatment in the hospital and was unable to return to work for three days.

Captain Joseph McFadden urges passengers to avoid sitting near exit doors, saying it allows thieves to easily snatch purses and phones and make a quick getaway.

McFadden says the attack caught on tape shows a second suspect, a 17-year-old, who acted as lookout.

Investigators say the suspects targeted Asian females in all five robberies.

“They're opportunistic. They're going on the Muni line. They're striking fast, quick and they're getting out of there," said Cpt. McFadden.

The victim has a message for her teenage attacker, “He’s so young, why he do like that? He should go to college. He should go to school to learn more, to help people, to help the community.”

She goes on to tell KTVU that she has been so scared, she is unable to sleep and no longer takes public transit to and from work. 

Police are asking anyone who witnessed any of the five robberies to please contact them.