A Juneau teen died Sunday after being stricken with heat exhaustion on a trail in Phoenix.

Kevin Walkenford, 14, was hiking with his mother, Yvonne Davenport, his aunt and a cousin when he collapsed near the end of a four-and-a-half-hour hike in the South Mountain Park and Preserve.

Paramedics were called to the trail at about 11:30 a.m. Sunday. It took them about a half hour to reach the boy, who was in extremely critical condition when they arrived, Phoenix Fire Department Capt. Hugh Chase said.

Walkenford was treated for heat exhaustion at the scene then transported to the Maricopa Medical Center in Phoenix, where he was pronounced dead Sunday afternoon.

Walkenford lived in Juneau with his father, Scott Walkenford. He was in Phoenix visiting his mother.

Arizona media reported Sunday that the hiking group had run out of water, but Chase said Monday that they treated the boy with their remaining water after he collapsed on the trail. They tried to get Kevin to drink and poured some of it on his skin and clothes, which is the proper treatment for heat exhaustion, Chase said.

"They all had bottles of water," Chase said.

Chris Walkenford, a Juneau resident and Kevin's uncle, said the boy had hiked on the trail with family members many times in the past.

Kevin Walkenford was born in Phoenix and moved to Juneau at age 6. He finished eighth grade at Floyd Dryden Middle School this spring and was to begin high school at Thunder Mountain this fall.

He traveled to Phoenix in June with his younger sister for the summer school break.

"He was a great kid," his uncle said.

Known for his humor and outgoing personality, he loved being outside and playing with his siblings and cousins in Juneau, Chris Walkenford said. He also played baseball and soccer.

The Phoenix area had been experiencing a heat wave since mid-July, according to the National Weather Service. High temperatures in the preserve were about 110 degrees on Sunday.

The Phoenix Fire Department has responded to about 90 heat-related emergencies so far this month, Chase said. The illness is caused by dehydration and rising body temperature.

Heat exhaustion is characterized by sweating, nausea and pale skin due to the body shunting blood to vital organs. Exhaustion can progress to heat stroke, when patients become lethargic, have very low blood pressure or lose consciousness.

"Once that cycle is started it's almost impossible to bring someone out of it," Chase said.

Kevin had passed out on the trail before anyone called 911, said Chris Walkenford, who had spoken with family members with him at the time. The boy regained consciousness quickly, but was unable to get up. His mother held his head and tried to give him water while they waited for emergency responders to arrive.

Responders gave him oxygen and intravenous fluid, but Kevin lost consciousness on the way to the hospital and they started CPR, Chase said. He called the situation "a terrible scenario of circumstances" since the boy was far from help and, besides water and potentially shade, had no way of getting relief from the sun and heat.

Chase said kids can compensate for heat exhaustion for a long time and then crash, going through the stages of heat-related illness quickly.

"Kids just go until they collapse," he said.

Last year, there were nearly 30 deaths due to heat-related emergencies in Phoenix.

A donation fund has been set up at Alaska USA to help pay for funeral expenses. The family will announce memorial service information at a later date.