Christopher Kulish, a 62-year-old Boulder attorney, died Monday at a camp below the summit during his descent. The cause isn't yet known, said his brother, Mark Kulish of Denver.
Christopher Kulish had just reached the top of Everest with a small group after crowds of hundreds of climbers congested the 29,035-foot (8,850-meter) peak last week, his brother said.
WATCH: Video shows line of climbers scaling Everest
"He saw his last sunrise from the highest peak on Earth. At that instant, he became a member of the '7 Summit Club,' having scaled the highest peak on each continent," Mark Kulish said in a statement.
He described his brother as an attorney in his "day job" who was "an inveterate climber of peaks in Colorado, the West and the world over."
"He passed away doing what he loved, after returning to the next camp below the peak," Mark Kulish said.
About half a dozen climbers died on Everest last week, including Don Cash of Utah, who also had fulfilled his dream of climbing the highest mountains on each continent. Kulish and Cash are the only Americans to die this season among 11 deaths so far, ABC News reports.
Most of them died while descending from the summit during only a few windows of good weather each May. To reach and then descend the summit, climbers must wait for good weather, resulting in a "rush hour-like traffic jam," ABC News explains. The longer wait times force climbers to spend more time in the so-called "death zone," where oxygen tanks can run out.
Most are believed to have suffered from altitude sickness, which is caused by low amounts of oxygen at high elevation and can cause headaches, vomiting, shortness of breath and mental confusion.
There are 41 teams with a total of 378 climbers permitted to scale Everest during the spring climbing season. An equal number of Nepalese guides are helping them get to the top.
Christopher Kulish also is survived by his mother, Betty Kulish, and a sister, Claudia.
The ABC Owned Television Stations contributed to this report.