An 80-year-old man died Sunday in the Grand Canyon after his boat flipped and dropped him into rapids along the Colorado River, park officials said. His death marked the fifth fatality recorded in the Arizona national park in less than one month. 

Rangers received word from a tourist group traversing the river that an elderly man had fallen in because his boat turned over at a section of the waterway called Fossil Rapid, according to the National Park Service. The agency said members of the group reached out to the Grand Canyon Regional Communications Center at around 3:40 p.m. Sunday afternoon by way of a satellite phone call. At the time, they said attempts to perform CPR on the man were underway. Neither the people in that tour group, nor park rangers who traveled by helicopter to the scene, were able to revive the man, whose identity hasn’t been shared with the public. 

The National Park Service said Tuesday that it was investigating the circumstances around his death in coordination with the Coconino County Medical Examiner. CBS News contacted a spokesperson for Grand Canyon National Park for more information or comment but did not receive an immediate response.

Sunday’s incident came on the heels of four other fatalities that have occurred in the Grand Canyon since July 31, and on the same day another tourist was found dead in the Colorado River.

The body of 33-year-old Chenoa Nickerson, of Gilbert, Arizona, was located Sunday by a group of visitors on a commercial river trip, according to park officials. She had been reported missing several days earlier after being swept away in a flash flood that hit Havasu Canyon, almost 20 miles from where she was found.

Earlier in August, officials said another woman was found dead about 150 feet below a section of the Grand Canyon rim called Twin Overlooks. She was identified as 20-year-old Leticia Castillo, of Albuquerque. Officials said when they located the body that she had likely been missing for three days.  

Not long before Castillo was believed to have entered the Grand Canyon, park officials said that rangers had discovered the body of a BASE jumper who apparently fell to his death after intending to leap from a spot along the South Rim of the park called Yavapai Point — which towers roughly 4,600 feet above the ground-level river that cuts through the canyon. His body was found beside a deployed parachute roughly 500 feet below the rim. The man’s identity wasn’t revealed. Officials said they’d opened a probe into his death and reiterated that BASE jumping, a particularly extreme take on typical parachuting that can be deadly, is illegal in the Grand Canyon.  

One visitor died at the tail-end of July after accidentally falling off the edge of the canyon near Pipe Creek Overlook, according to the national park. That person was identified as Abel Joseph Mejia, a 20-year-old from North Carolina, whose body was found 400 feet below the rim. Officials said people should remain at least six feet away from the edge of the Grand Canyon rim when visiting the park.

At least 13 people have died at Grand Canyon National Park so far this year.