Transcript for Roger the ripped kangaroo's caretaker: 'Roger and I were best mates'

This is my little boy, Roger. Hey, Roger, you're on TV tonight. Reporter: His physique was astonishing, bulging shoulders, ripped arms and shredded abs. He towered at 6'7" on his hind legs and weighed nearly 200 pounds. This 2015 photo of him crushing a metal can went viral, making him famous around the world as he leapt to stardom. But just days ago, Roger the red kangaroo died of old age at the kangaroo sanctuary in Australia where he spent most of his life. He was 12 years old. In a tweet, Australia's official tourism account called the beloved kangaroo a true icon. It's a very sad day here today. For we have lost our beautiful boy, Roger. Reporter: Chris Barnes, the founder of the refuge, posting this heartfelt message to Facebook. Roger grew up to be a kangaroo that people from all over the world have grown to love. Reporter: In 2006, Barnes found Roger in his mother's pouch, alive but orphaned after a car had struck and killed her. We spoke to Barnes about that moment over facetime. There's a real cute little baby, a little Joey, and like all our joeys, we carry them around in a little pillow case. Reporter: Inspired, Barnes created a safe haven for kangaroos in Australia's northern territory, seen in the national geographic wild series, kangaroo Dundee. He would grow to the sanctuary's alpha male. He had a Har em of 12 wives and when they've got that harem, they want to defend them from everyone. Reporter: Barnes and Roger had a turbulent relationship. I was Roger's mom. And that's why he's got no fear of people. Reporter: Barnes playing the role of the parent at times had to lock Roger in a pen to keep him away from other visitors. Roger, the temperamental son sometimes let his brute strength and alpha aggression get the best of him. I was out in the sanctuary and my old mate, Roger, clocked eyes on me and he wanted a piece of me. There's no doubt about that. So I bolted. I was running faster than usain bolt and he was right behind me and I turned around, trying to catch a sight of Roger, where he was, and at that time, I fell over a termite mound hidden in the grass, and straight away, I knew I had done some damage. Reporter: But that didn't stop Roger from being adored and ogled by fans across the world online and in person. The sanctuary attracting visitors from around the world, a sign experts say brings awareness to conservation efforts. So I think when you have these animals that become these social media giants, people can relate to them. Reporter: When Roger and his biceps burst into the public eye, he joined a long list of internet famous animals who bring attention to good causes and in some cases make big money. Like Bebe, the famous panda cub born in 2015 at the national zoo in Washington, D.C. Having the pandas there at the zoo are a huge draw. It drives the gate. The smithsonian does a tremendous amount of research working with pandas, knowledge that we can apply to protecting those animals in the wild, knowledge they can share with the research institutions in China. Reporter: And in April of 2017, millions of Americans were glued to a live stream waiting anxiously for April the giraffe to give birth. Cincinnati has thousands of people flocking to see Fiona the hippo. Fiona first gained popularity in the womb. She was the first nile hippo to be born in the zoo in 75 years. When she made her debut six weeks prematurely. Her lungs weren't strong enough and neither was her overall muscle control. Reporter: The zoo documented her struggle to survive on Facebook as the world watched her learn to stand. Big girl. Reporter: Swim, even take her first step. There you are. Let's put her back. When people care about an animal, tugs at their heart strings so they've give money to these organizations that are doing work to preserve those animals. Roger's favorite food in the whole world. Reporter: Back in Australia, Roger spent his final years in a more mellow state. Roger and I were best mates. We used to lie down out in the grass together and his aggressive days were over because he was getting older and older. Reporter: Relinquishing the alpha role to his son where the legacy of the muscle bound kangaroo will live on. You're such a beautiful old

This transcript has been automatically generated and may not be 100% accurate.