A Castle Rock, Colorado, father of three and retired West Metro firefighter, died last week while vacationing with his family in Hilo, Hawaii.

Hawaii Police say Greg Durocher became unresponsive after scuba diving. A coroner's inquest is underway to determine the cause of his death. His family will be returning to Colorado on Monday.

From Castle Rock to Lakewood, loved ones are mourning and remembering the 51-year-old father, husband and friend.

"Couldn't be a better human being," said Dean Wahl, retired West Metro fire captain.

Pictures and memories are all Wahl has left of a man he fought fires with and called a friend.

"Greg's the guy in the white T-shirt, and this was a four-man crew that was sent to Texas for the Space Shuttle Columbia recovery," Wahl said, while flipping through a West Metro Fire photo book from the years 2005 to 2015.

A Boulder native, Greg Durocher worked under Wahl at West Metro Fire, where Wahl says Durocher was one of the first members of the bike medic team.

"Very conscientious, usually didn't have to ask him to do anything because by the time you asked, it was already done. That's just the kind of guy that he was," Wahl said. "He was just a great person, so personable and gregarious and out with the public. He was the best guy to have there."

Durocher met and married his wife, Amie, while working for West Metro Fire Rescue.

"While we were working together, he met Amie, love of his life, head over heels," Wahl said. "The crew actually was able to plan his proposal. We all knew he was getting married before Amie knew."

Wahl says Durocher planned an elaborate proposal at Zoo Lights.

"He had a little thing on his clipboard and he clicked it, it said 'Amie, will you marry me,'" Wahl said. "That's the kind of guy he was, he liked to keep things fresh, really liked to make things exciting."

After the couple were married in 2003, they welcomed three children: two sons and a daughter.

"Nothing made his face light up more than going to events and being with his kids," Wahl said.

Durocher eventually retired from the fire service and launched a car seat safety company with Amie called .

Amie Durocher tells CBS Colorado the family moved from Washington Park to Castle Rock in 2021.

In May, their daughter graduated from Castle View High School. With one child on the way to college and another heading to boot camp, Amie says the family took a "maybe-this-is-our-last-family-vacation" vacation. Sadly, the family didn't know how true that statement would be.

While scuba diving in Hilo on June 30, tragedy struck.

When Durocher reached the surface after scuba diving, Amie says he complained he couldn't breathe and lost consciousness. She says their son and the dive master pulled Durocher out and started chest compressions, but Hawaii Police say he was pronounced dead at a local hospital.

While the  said the family was taking a scuba diving lesson, Amie says it was not a lesson but a scheduled dive. She says Durocher was advanced open water certified and had more than 50 dives under his belt, and that the whole family had diving experience and certifications.

"Absolutely terrible, terrible," Wahl said. "I can't even imagine the tragedy, and then to be that far away from the mainland."

When Amie texted Wahl with the news, he was in shock.

"Fifty-one years old is way too young," Wahl said. "I wake up every morning and I still can't believe. You know, this kid was fit."

In the last week, Wahl says many former firefighters have reached out to him about Durocher's passing, expressing disbelief and sadness.

As he mourns his friend, Wahl says there's one thing that stands out as Durocher's legacy.

"How dedicated he was to his family. He was a great firefighter, but that was a career; the real dedication was to his family, to his wife, to his children," Wahl said.

Durocher's tragic passing serves as a lesson to live like he did.

"Don't wait, don't put off doing things you want to do with your life. Take advantage of being with your family. Kiss your wife and your kids before you leave for work," Wahl said.

Amie Durocher says her husband was "a wonderful man and father and personal development coach (along with running Safe Ride 4 Kids, he taught and consulted for the Denver SBDC). He wasn't much for being in the spotlight. He was a Colorado native. He was born in Boulder. He worked for West Metro Fire for 13 years and volunteered at Eldorado Springs Fire (when that still existed) for five years before that."

A spokesperson for West Metro Fire Protection District shared a statement about Durocher and his passing:

"Greg was a firefighter with West Metro from 1998 to 2011. He served 13 years with us. Before that he was a volunteer firefighter for five years. He was a well-respected member of our staff, and had a passion for safety for children. He left the fire service to start his own business in car seat safety. You can see this on his LinkedIn profile. The name of the company is Safe Ride 4 Kids. He was an engineer when he left the fire service. Everyone here who knew Greg is saddened to hear of his passing. And our thoughts are with his family."