The family of a mother who died six weeks after being assaulted at a bus stop in Birmingham are appealing for help to catch her attackers.
Ms Cullum was hit after arguing with four youths at the bus stop
Tracey Cullum, 30, from Selly Oak, confronted a group of teenagers after they jumped the queue, police said.
She was then punched in front of her 12-year-old son and treated in hospital for a broken ankle. She later died of a coronary embolism.
West Midlands Police said they were linking her death with the attack.
Ms Cullum's partner, Mark Holliday, said it was in her nature to tackle anti-social behaviour.
"It was an honour to know her. She will be sadly missed," he said.
"I would like to appeal to the person who did this to come forward.
"I believe when you have done something like this you will not have realised the consequences of your own actions."
Det Ch Insp Jan Thomas West told the BBC officers were looking at CCTV footage and had spoken to a number of witnesses.
Mr Holliday said it was 'an honour' to know Ms Cullum
Those involved in the incident, thought to number between four and five, are described as young black males.
The main offender who attacked Ms Cullum is believed to be aged 17 to 20, between 5ft 6in and 6ft tall and was wearing a dark hooded jacket.
"Clearly from the post mortem-examination, I am satisfied we can link the assault and resulting injuries to Tracie's death," Ms Thomas West said.
"The investigation was under way from the original assault and now we have more officers involved."
Ms Cullum was waiting for the number 29 bus on Colmore Row in the city centre on the evening of 2 July with her son, a friend and three other children when she was attacked.
She was confirmed dead at Birmingham's Selly Oak hospital on 12 July after falling ill at home.
A post-mortem examination confirmed she died of a coronary embolism.