A high school cross-country runner in Tennessee has died while out on a run in his neighborhood.

The student, identified by the Cheatham County Sheriff’s Office to local news outlets as 15-year-old Tristen Franklin, went to Sycamore High School in Pleasant View, about 20 miles northwest of Nashville. 

Tim Adkins, a Cheatham County Schools district spokesperson, confirmed the student’s death to The Tennessean, part of the USA TODAY Network, on Wednesday, and said that he was at home and running in his neighborhood when he died.

The district was “deeply saddened” by his passing, Adkins said in a statement. “Our heartfelt thoughts and prayers go out to the student’s family and friends during this difficult time. The impact of such a loss is immeasurable.”

The cause of Tristen's death remains unclear.

Neighbors witnessed teen's collapse, reports say

Troy Simpkins, Tristen's neighbor, told WBTV that he often saw the boy running his normal route in the afternoons, and that the two would greet each other.

He said he saw Tristen on the move Tuesday, but didn't think anything of it until his husband got a call from another neighbor, who saw the teen collapse. They immediately called 911 for help, but it was too late, WBTV reported.

“My heart just goes out to them. I mean, it is so sad, " Simpkins told the station. "He was so young and had his whole life ahead of him. Tell the people in your life how much you love them.”

Student athletes delt with ‘high temperatures’ this week

The cross country season was just getting started for Tristen and other students on his team. Student athletes across all sports dealt with “high temperatures” in the area on Tuesday.

The Cheatham County School District was following a Tennessee Secondary School Athletic Association heat policy in an attempt to ensure the health and safety of all student athletes. 

Sycamore High School was investigating what procedures were in place for after school activities that were held outside on Tuesday and Wednesday. 

Temperatures approached record highs in middle Tennessee, according to the National Weather Service in Nashville. The agency reported highs of 97 degrees on Monday and 100 degrees on Tuesday at Cheatham Dam, which is about 17 miles from Pleasant View, where Sycamore High is located. 

Triple-digit temperatures were expected to remain in the forecast through Thursday, according to The Tennessean. The heat is expected to subside a little by Friday.