The "Good Samaritan" killed in the middle of a Melbourne street at the weekend has been remembered as a "lovely, lovely bloke", who leaves behind a wife and two young daughters.

The 46-year-old was stabbed to death after he allegedly tried to break up a fight between another man and his pregnant girlfriend on Blackshaws Road, Altona North, on Sunday afternoon.

The victim did not know the couple, Detective Senior Sergeant Stuart Bailey said.

"He stopped, left his vehicle and has approached the two and was fatally stabbed as a result," Detective Senior Sergeant Bailey said.

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Passers-by performed CPR on the injured man before paramedics arrived, but he died at the scene.

Fairfax Media has not published the victim's name at his family's request.

The man's colleague Nicole Waymouth remembered the 46-year-old warehouse worker as a "lovely, lovely man".

"There's no doubt he'll be greatly missed here at work," she said.

Ms Waymouth said her former colleague would often come to work with a new story about his two daughters, aged 14 months and 14 years.

"He loved his family, absolutely loved his family. His two daughters and his wife were everything to him," she said.

"He would come in weekly with a video or some sort of story to tell us about his youngest daughter, or older daughter...

"He was just a really down-to-earth family guy, he was straight up, he was a very hard worker. He worked for us for probably about four and a half to five years, but probably did the work of 10 years. He was one of the nice guys."

The man's friend, known only as Tim, remembered the man as a "great bloke".

"He do anything for anybody," he told Fairfax Radio 3AW.

"He was the best man at my wedding a few years back."

Tim said his friend enjoyed martial arts and had been taking taekwondo lessons with is eldest daughter.

"He's got a young family ... just renovated his house, he was going to start doing his yard," he said.

The alleged killer – a 21-year-old man from Carlton North – was arrested on Tuesday after a nine-hour stand-off with police at the home of his girlfriend's parents. He was due to be charged on Tuesday afternoon.

His girlfriend, who is 22 weeks pregnant, was assessed by paramedics at the scene before being taken to the St Kilda Road police station to be questioned by detectives.