A hiker on Electric Peak and an angler fishing the Yellowstone River died in Yellowstone National Park this week.

The hiker, Joseph Austin Parker, 23, was reported missing Tuesday evening after failing to return from a trek to Electric Peak, a nearly 11,000-foot peak in the northwestern corner of the park. Park officials say the last contact made by the young man was a phone call to friends Tuesday afternoon during which he told them lightning in the area convinced him to head back to the trailhead.

An aerial search Wednesday by both airplane and helicopter and a ground search by teams in 4-wheel-drive vehicles, on horseback, and on foot did not turn up any clues to the man’s whereabouts. On Thursday morning, however, searchers found his body below the summit of Electric Peak. The cause of death is under investigation.

Originally from Valdosta, Georgia, Mr. Parker was working at a local Gardiner, Montana, business, according to a park release.

On Wednesday, a 73-year-old man from southwest Montana died after losing his footing while fishing in the Yellowstone River near the Nez Perce picnic ground in the Mud Volcano area. Witnesses told rangers the man "lost his footing in chest-deep water while attempting to cross the river and was carried approximately 200 yards downstream in the swift current," park officials said.

"Another visitor ran downstream and pulled the unconscious man ashore and initiated CPR. Park rangers and medical staff were notified and responded but were unable to revive the victim," a park release said.

The cause of death remains under investigation, and the man's name was being withheld pending completion of notification of family members.