Devastated colleagues are mourning the death of a young paramedic killed outside a Sydney fast food outlet, as it emerged his partner is expecting a second child.

The 29-year-old, named by media outlets as Steven Tougher, was fatally stabbed outside Campbelltown McDonald’s while he and a workmate took a break towards the end of their night shift about 5.30am on Friday.

The colleague activated a duress alarm, sparking a police response in which a 21-year-old man wielding a knife was tasered and arrested. No charges have been laid.

The victim, who had been working for the ambulance service for about a year, was assisted by witnesses at the scene but died shortly after arriving at Liverpool Hospital.

“The surgeons … worked valiantly, albeit futile in this instance, to support our colleague,” NSW Ambulance Commissioner Dominic Morgan said.

The slain man’s father said his son always wanted to be a paramedic and had just been posted to southwest Sydney, Dr Morgan said.

He was reportedly on a break, waiting for coffee, when he was attacked.

“On arrival police were confronted by a 21-year-old man from Raby, who was armed with a knife,” NSW Police Deputy Commissioner Mal Lanyon said.

“In order to render assistance to paramedics on the scene, police were forced to use a taser and subsequently arrested that 21-year-old male.”

The tragic paramedic was taken to Liverpool Hospital for treatment but died of his injuries later on Friday morning.

In custody

The 21-year-old man was taken to Campbelltown Police Station for questioning. He was still assisting police later on Friday.

Officers have established a crime scene and a homicide investigation is under way.

NSW Ambulance Commissioner Dominic Morgan said the man’s death was a tragic loss.

“You can imagine this is an extremely difficult time for his young family and the NSW Ambulance broader family,” he said.

“He wanted nothing more than to serve his community. This is a time of recognising and grieving with the paramedic’s colleagues and family at a very difficult time,” Mr Morgan said.

He said the man’s parents, wife and sister were “beside themselves after this tragic loss”.

“Personally, it’s very difficult to process any person just going to work to do their job, let alone a paramedic who puts themselves on the line, to not come home is a tragedy and almost inconceivable to work through on any level,” he said.

NSW Health Secretary Susan Pearce wept as she paid tribute to the man and his team.

‘Incomprehensible to us’

“I’d like to extend my deepest condolences to the loved ones, the wife and family of our paramedic,” she said.

“The health system is one big family and to lose someone in this way is incomprehensible to us.”

Speaking before the man’s death, NSW Premier Chris Minns said the incident was a reminder of the job’s dangers.

“It’s a reminder that it is a very dangerous and difficult job that requires enormous courage to put on that uniform every day and serve the people of NSW,” he said.

“My thoughts are with every paramedic in NSW.”

Prime Minister Anthony Albanese also paid tribute, describing the man’s death as as “shocking as it is tragic”.

“To every front-line worker, you are valued. You keep us safe. You deserve to be safe at work,” he said in a social media post.

No charges have yet been laid.

Police have asked for people who saw a blue Honda Jazz sedan in the Ingleburn area before Friday’s incident to contact them. Anyone with information is urged to contact Crime Stoppers on 1800 333 000.

– with AAP