At least 11 people have died on Mount Everest this year (Reuters)

It was the final climb on his quest to reach the highest summit on all seven continents. When Christopher Kulish finally reached Mount Everest's 29,035-foot peak, he joined an elite group known as the "Seven Summits Club."

But the 62-year-old Colorado attorney died Monday after returning to the first camp below the mountain's summit. He's the second American to die in the past week after reaching Everest's highest point.

His family believes the cause was cardiac arrest, according to the Denver Post.

"He saw his last sunrise from the highest peak on Earth," his brother, Mark Kulish, said in a statement to The Denver Post. "We are heartbroken at this news."

Last week, 55-year-old Donald Lynn Cash of Utah collapsed and died just after reaching the Everest peak. He, too, had reached the highest point on all seven continents.

At least 11 people have died on Mount Everest this year.

The deaths come amid reports of overcrowding on the popular mountain. The Nepali government granted 381 permits to climb Everest this year, a number that doesn't include guides who are on the mountain as well. For some climbers, that traffic has meant longer wait times - some told the Himalayan Times the wait has exceeded two hours between the last camp and the peak.

There's also been debate over whether the bottleneck is a result of more inexperienced climbers crowding the mountain. Mountaineering experts suggest that experience level and various factors causing crowding are contributing to this season's death rate.

Mountaineer Vanessa O'Brien, who has also climbed the seven summits, said when there's a crowd, being a more experienced climber won't help.

"It doesn't matter if you're the best race car driver in the world. If you're stuck in traffic, you're struck in traffic," she said in an interview.

And when a climber is stuck in Everest traffic, "their body is starting to deteriorate." O'Brien, who set a record as the fastest woman to reach the highest peak on every continent, also said the descent is often harder than the climb.

"You have given up so much energy to get up there and now you're only halfway," she said.

Climbing expert Alan Arnette said there's no simple explanation for the string of deaths. He said weather that has led to a shorter climbing season is one factor causing overcrowding. He also said the cost to climb Mount Everest has decreased, which means more people are making the journey. He urged the governments in charge of granting permits to limit how many people can be on the mountain at once.

"The solution lies in governments having strict qualification on who can guide and climb and not simply accepting their money without question," Arnette said in an email. "You have to qualify for the Boston Marathon, but not to climb the world's highest peak. Therein lies the problem."

Still, Kulish was no beginner. His family said he'd been climbing mountains for five decades. He arrived at the base camp nearly two months before his climb so he could give himself time to adapt to the conditions. When he made his journey, his family said he was climbing with a small group in almost ideal conditions after some of the congestion had cleared, The Denver Post reports.

He was a partner in the Boulder office of law firm Holland & Hart from 2002 to 2009 before starting his own practice. In a statement, the firm said Kulish "will be remembered as a friend and an excellent patent attorney. We are deeply saddened to learn of his death, and extend our sympathies to his family and friends."

His brother described being an attorney as a "day job" for Kulish. Climbing was his passion.

"He was an inveterate climber of peaks in Colorado, the West and the world over," Mark Kulish said. "He passed away doing what he loved."