When seven Penrhos College girls saw a boy being robbed of his phone at a busy train station, they knew they had to act.
While some comforted the young Aquinas College student, the others sprang into action - one called the police and two others raced after the teenage robber at Canning Bridge station, trying to snap photographs of him on their phones before he turned on them and gave chase.
But it was the quick thinking of the girls, who cannot be named for legal reasons, to alert authorities that allowed transit guards to intercept the alleged thief yesterday morning and hand him over to police.
The 15-year-old has been charged with stealing and was refused bail. He is expected to face Perth Children's Court today.
A Year 11 Penrhos student said she knew something was wrong when she saw the Aquinas boy's face after his interaction with the stranger during peak hour.
"The school has always told us to help where we can without putting ourselves in danger," the teenage girl said.
"I asked him, 'Are you OK?' . . . he said (the accused) had asked for money but he didn't have any, so he gave him his phone because he was afraid he'd get hurt.
"That's when I called police."
After the alleged thief returned to get the stolen phone's password, two girls followed him downstairs to the train platform to take a photo to send to police.
"He has seen them and chased them back up the stairs to scare them off," the Penrhos student said.
"Then he got on the train to Perth."
A Public Transport Authority spokeswoman said the girls' description of the offender was quickly relayed to the PTA's central monitoring room via police.
Through the network's 1400 cameras the teen was quickly identified and apprehended as he left the train at the Esplanade train station.
The Penrhos student said she too had previously been approached at the train station and knew what the boy was going through.
"We just put ourselves in his shoes," she said.
"If it happened to one of us, we would want someone to help.
"I'm really happy the boy got his phone back."
Penrhos principal Meg Melville said the school was extremely proud of how the students acted. "They showed excellent judgment in assisting the young boy in need," she said.