Paul Schmidt, 37, who worked for a moving company, died on Sunday after the alleged daylight attack in Vancouver.
His mother said her son’s fiancée, Ashley Umali, was inside the cafe while he waited outside with their daughter.
She said Umali told her the incident started because the alleged attacker was using a vape.
“He was just trying to protect his daughter.”
Vancouver Police said there was a “brief altercation” and Inderdeep Singh Gosal, 32, has been charged with second-degree murder.
They’re appealing for witnesses and any footage from the “dozens” of people who might have seen what happened.
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“Investigators do not believe the victim and suspect knew each other, however the circumstances that led up to the fatal stabbing remain under investigation,” police said in statement.
Footage of the attack was posted online but family have pleaded with people not to watch it.
Mr Schmidt’s sister said in a social media post it made her “sick”.
“Someone took my brother’s life yesterday and another person filmed it (do NOT watch) instead of calling the police and worse off posted it on social media very clearly for views,” she said.
British Colombia government Public Safety Minister Mike Farnworth said what happened was “absolutely horrific”.