Irwin was a star of the Crocodile Hunter television series and was popular by the name 'Crocodile Hunter'. He was stabbed ‘hundreds of times' by the stingray's barb as the pair stood chest-deep in water.
Justin Lyons was filming a documentary with Irwin off the coast of northern Queensland when tragedy struck in 2006.
After spotting a giant stingray, they got into the water and filmed the eight-foot creature for some time before it suddenly attacked.
"All of a sudden it propped on its front and started stabbing wildly with its tail, hundreds of strikes in a few seconds. It wasn't until I panned the camera back [and saw] that Steve was standing in a huge pool of blood that I realised something had gone wrong", Lyons told Channel Ten's Studio 10 programme.
It was only after Lyons got Irwin back on the boat that he was able to see the seriousness of his injuries.
"The stingray's jagged barb went through his chest ‘like hot butter'. He had about a two-inch injury over his heart with blood-fluid coming out of it. He was in extraordinary pain. [The stingrays] have got venom on their barb, so I'm sure it was excruciatingly painful", he said.
"Even if we'd been able to get him into an emergency ward at that moment, we probably wouldn't have been able to save him because the damage to his heart was massive. As we're motoring back, I'm screaming at one of the other crew in the boat to put their hand over the wound and we're saying to him things like, "Think of your kids, Steve. Hang on, hang on, hang on", Lyons said.
"He just sort of calmly looked up at me and said, "I'm dying." And that was the last thing he said", Lyons added.