FOURTEEN-year-old Sidonie Thompson had so much to live for.

An extremely bright, talented and kind girl, her violent death has horrified and traumatised family, friends, neighbours and police.

The victim of what is suspected to be a murder-suicide yesterday at her home in the affluent suburb of Paddington, in Brisbane's inner-west, the Year 10 Sommerville House student had dreamed of being a neurosurgeon.

The discovery was made by her father, who had returned home from a game of tennis about 7am to find the lifeless body of his only daughter and his only son missing.

He found his daughter's body in her bedroom suffering slash wounds believed to be caused by an axe. Neighbours reported hearing screams about 6.30am.

Across town, at about the same time, traffic was banked up around the Story Bridge after Sidonie's 48-year-old mother stopped her car on the side of the road - with her 12-year-old son inside it - and jumped to her death.

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

"Four construction workers were there and one was trying to talk to the boy and the other three were looking down where it happened. The boy was sitting there looking at him and he was expressionless - like he was in a trance."

Police were still at the home late yesterday after spending the day scouring the property."There's strong indications that both the incidents are linked," Detective Inspector Tony Duncan said.

As details of the tragedy began to unfold, tributes started to pour in for Sidonie, known as "Sid" by her friends at the exclusive Somerville House school.

Sidonie, a talented music student, would have turned 15 in November. She had wanted to be a neurosurgeon.

Somerville House principal Florence Kearney said the school was deeply saddened, and described Sidonie as a smart and popular student.

"(She) was friendly, engaging ... well respected and very popular with staff and students and she'll be sadly missed," she said.

More than 4100 people joined a Facebook memorial page last night for Sidonie, with one contributor, Lexi Mckee, describing her as "such a sweet girl".

"Rest in peace, Sidonie, your life will always be cherished x," Hannah George wrote.

"You have no idea how much we are going to miss you," Bronte Poon added.

Those who lashed out at the woman were urged by others to show restraint.

"Please, out of respect, just show your compassion for her friends and family and celebrate the way she lived, instead of debating how she died," wrote friend Erin Matsuura-Miller.

"There's no justifying what she did, but her mum was really unwell, so maybe you should think before you speak," Alana Bethune wrote.

Year 10 students at Sidonie's school were sent home yesterday morning, many seen leaving in tears. Mrs Kearney said a memorial service would be held.

"We're just managing the students in the best way we can under these circumstances. We have counsellors on call. She's had a long association with the school having started here a number of years ago."

Kids Helpline: 1800 55 1800 | www.kidshelp.com.au.

Parentline: 1300 30 1300 | www.parentline.com.au

Lifeline: 13 11 14 | www.lifeline.org.au

Beyond Blue: 1300 22 46 36 | www.beyondblue.org.au