The Brisbane police theory that the fatal axing of a teenage girl in Paddington on Wednesday and the bridge suicide of a woman from Story Bridge are linked appears to be correct.

The woman is now the suspect in the slaying of her daughter, 14-year-old Sidonie Thompson, who was a remembered for being a bright student and dreamt of becoming a neurosurgeon.

Neighbors recalled hearing screams from the Thompson house at about 6:30 a.m. After about 30 minutes, the father, a businessman, returned home from a tennis lesson and discovered the body of Sidonie inside her bedroom with multiple stabs. He made a triple-O call to report the incident and seek help.

Minutes earlier Brisbane police got a call about the suicide at Story Bridge. The 48-year-old woman, Sidonie's mother, stopped the vehicle by the road side, got out and jumped from the bridge, a witness said.

"It looked like it was just a broken-down car, I think she just flicked on the hazard light and off she went to jump over the bridge," the witness told the Herald Sun.

The witness added that one of four construction workers who saw the incident tried to talk to a 12-year-old boy who was left inside the car. The witnesses said the boy was expressionless and appeared like he was in a trance.

The boy, Sidonie's brother, was brought to a hospital for treatment for minor injuries.

Police spent Wednesday inside the Thompson residence looking for further evidence and to confirm the link between the two deaths.

Sidonie was supposed to turn 15 in November and was a talented Year 10 music student at an exclusive school. Somerville House School Principal Florence Kearney described Sidonie as a friendly, engaging, well respected and very popular student.

A Facebook memorial page created for Sidonie attracted over 4,100 people. Some posters lashed at Sidonie's mother - a company director - who is suspected of being behind her daughter's death. One poster said that while there is no justification for what the mother did, she pointed out that the woman was apparently troubled.

The Thompsons lived a comfortable life. They moved in Carrington Street in 2001 after they purchased the house for $1.3 million. They also own several properties in Woolloongabba and Coorparoo which have combined worth of over $1.2 million.

The Brisbane police is preparing its report for submission to the coroner.