Australian cop was in World Trade Centre when the first plane hit on ...

Twenty-two years ago, an Australian police officer in the US found himself at the epicentre of one of the deadliest attacks in modern history, on his first day of anti-terrorism training.

Now-retired New South Wales police officer Patrick Stafford had just begun a work trip to train with the New York Police Department on September 11, 2001.

The experience informed the rest of his career, and now he is speaking publicly about the day that changed his life, and countless others, for the first time.

"I was in the World Trade Centre for about 15, 20 minutes," Stafford told 9News.

"Leaving the building when the first plane had already crashed into Tower 1 above us." 

But he said he didn't notice.

About ten minutes later after arriving at the NYPD office in Brooklyn, Stafford's attention was glued to a television.

"I called out to the NYPD staff who were sitting behind me in various cubicles that did they know the World Trade Centre was on fire."

As they all huddled around, they watched the second plane hit the south tower.

The emergency response immediately went into overdrive and every single first responder in the city was called in.

There was a mass evacuation and only firefighters, paramedics and police were allowed in the area, but roughly an hour later it all came down.

"When the tower collapsed, first tower one and soon after tower two the mood in the (NYPD) office got pretty violent… and they got pretty upset, they were tossing chairs, turning up tables, they were angry," Stafford said.

When he returned to Australia, the now-retired officer used his experience to teach others what to do and what not to do when the worst happens.

Stafford shared this insight with police across the country until he retired last July.