He was supposed to be shooting scenes along Australia’s Great Barrier Reef for a documentary he was making called Ocean’s Deadliest, but the waters there were too cloudy. Never one to fritter away an idle moment, the ever-energetic adventurer and Crocodile Hunter Steve Irwin decided to film a segment for his daughter Bindi’s upcoming wildlife show on the Discovery Kids channel.

In fact, he was kind of looking forward to it. “He was in such a good frame of mind,” says his longtime friend and producing partner John Stainton, who was with him Sept. 4 on the deck of Irwin’s 75-ft. research boat Croc One. “We sat together in the early hours, 5 a.m., 6 a.m., having a cup of tea, just talking about how good life was.”

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Anchored at Batt Reef off the resort town of Port Douglas in Queensland, Irwin, 44, slipped into the water with his cameraman to film a school of stingrays. For a man who had tussled with crocs, venomous snakes and other frightening creatures, this was going to be a leisurely swim. Better than most anyone, he knew that stingrays are so docile that they generally put up with the prying eyes and underwater cameras of amateur divers. Then it happened.

As he was snorkeling in waters no more than 10 feet deep, he passed above a bull ray, which can grow up to seven feet in diameter. For some reason it stopped, then suddenly whipped its razor-sharp tail directly up toward Irwin and plunged the barb deep into his chest, piercing the heart.

The cameras kept rolling. Irwin had gotten himself out of many a predicament before, and there was hope he might escape again. Not this time. Just seconds after pulling the barb out of his heart himself, he was pulled back onboard Croc One, where the crew tried desperately to stop the bleeding. Long before a rescue helicopter could arrive, he died. “He pulled [the barb] out,” said Stainton. “And the next minute he’s gone. That was it.”

Within hours of hearing the news, fans everywhere found ways to express their heartfelt grief. The Prime Minister of Australia offered to hold a state funeral for Irwin, and close friend Russell Crowe remembered him, saying, “He touched my heart. I believed in him. I loved him and I’ll be there for his family.” Even those who only knew Irwin from TV filed past his Queensland zoo on the Sunshine Coast and left flowers and notes of condolence.

It was a tragic, yet in some ways not wholly unexpected end for the adventurer. Irwin had been around animals from an early age. His father, Bob, 66, opened Australia Zoo in 1973, and his mother, Lyn, who died in a car accident in 2000, was a former nurse who cared for baby kangaroos and injured birds. Wrestling his first crocodile at 9 years old under his dad’s supervision, Irwin has said that working with animals was “in my genetic makeup.”

As a result he never shied away from getting snout-to-snout with even the most unfriendly beasts. “He’s like Tarzan meets Indiana Jones,” his wife of 14 years, Terri, 42, told PEOPLE in 2000. On his two Animal Planet shows Crocodile Hunter and Croc Files, Irwin, whispering closely to the camera in his thick Australian accent about whatever fascinating animal he was with, would often get within striking distance of his deadly costars. In one episode he even allowed a snake to repeatedly bite him on his thumb in order to document the biological repercussions.

But all that derring-do wasn’t just for ratings. Dubbing himself the “wildlife warrior,” his ultimate goal wasn’t to show off his bravado, he said, but to teach people to respect animals. “Our motto is conservation through exciting education – that’s the game,” Irwin told PEOPLE of his eco-awareness efforts.

His tactics certainly enthralled crowds. During one promotional appearance at Australia’s Alice Springs Reptile Centre in 2003, owner Rex Neindorf recalls introducing Irwin to a two-yard-long lizard called a perentie goanna. “I told him explicitly not to handle him and to use a broom, but Steve completely ignored me,” says Neindorf. “He ended up with about 10 incisor marks on his arm. There was blood everywhere. That was Steve the entertainer; he was a real showman.”

Of course that quality also brought Irwin much criticism, most notably in 2004, when he was filmed feeding a crocodile with one arm and holding 1-month-old son Bob in the other during a live show at his zoo. The footage was played over and over on newscasts, prompting Irwin to appear on the Today show, among other outlets, to defend his actions. “I would never, ever endanger my children,” he said, maintaining that he had the situation under control the whole time. “Despite what people thought of him, he was very safety conscious,” says friend Craig Adams-Maher, operations manager of Australian Reptile Park, who filmed a sea-snake segment with Irwin just a few days before his death. “His family was everything to him.”

And he was everything to them. Terri, an American who saw Irwin in action in 1991 during a visit to his zoo, married him just nine months after meeting him. “They were two of a kind,” says Terri’s mother, Julia Raines, who lives in Eugene, Ore. “They thought alike and both loved animals – it was fate.” As for their children Bindi Sue, 8, and Bob, 2, “they absolutely adored him; they thought he was the best.”

Terri heard the news about Irwin’s accident while on vacation with the kids in Tasmania and immediately flew home. “She has a long way to go as far as grieving is concerned; it’s so raw,” a family friend says of Terri, who remained in seclusion in the days following her husband’s death. “But she’s a tower of strength.”

Irwin had a particularly special kinship with Bindi. In the middle of Irwin’s Today interview, the little girl, then 5, hopped on Dad’s knee, stroking his face and hugging him as he spoke. Bindi has even become a fearless animal lover herself, frequently appearing on Dad’s show Croc Files, where she handles non-deadly snakes and lizards. And both she and Dad couldn’t wait for her upcoming Discovery Kids show, which now may not ever air.

Whether or not the project will continue is yet to be determined, but regardless, Bindi will likely continue her father’s conservation work. “We’ve got a fantastic chip off the block ready and raring to go,” says environmental organization Planet Ark founder and pal Jon Dee, who met Irwin in 2002. “Hopefully she’ll educate a whole new generation in the way her dad has.”

While he’s left behind a wildlife rescue mission at the Australia Zoo and a greater awareness of all creatures, “Steve’s greatest contribution was to his family,” says Mal Brough, a friend of Irwin’s and a minister in the federal government. Despite his tragic death, “I have no doubt that they will never let his legacy die.”