Teen National Guard trainee died of ‘undetectable and very rare heart abnormality’

Brianna and Alyssa Cahoon, 1st Battalion 34th Regiment . (1st Battalion 34th Regiment)

Doctors revealed the reason behind the unexpected death of a 17-year-old member of the Pennsylvania National Guard after she suffered a medical emergency during training on Aug. 20.  

Private First Class Alyssa Cahoon’s heart suddenly stopped due to a "completely undetectable and very rare heart abnormality," according to a post published on the Fort Jackson 1st Battalion, 34th Infantry Regiment’s Facebook page.  

Alyssa died on August 25 with her family by her bedside, according to an earlier Facebook post.  

It was also discovered that her twin sister, Brianna, who trained alongside Alyssa at Fort Jackson, has the same heart abnormality.  

"As tragic as this loss is, her sacrifice will save Brianna (her identical twin) who has the same heart abnormality but will now receive an internal defibrillator," the post continued.  

To honor Alyssa’s memory, her family is asking for soda tab donations to support the Ronald McDonald House Charities.  

"Tab collection is a fundraiser for The Ronald McDonald House and now Kisses for Aly will help them. Please help us save Kisses for Aly and save all your soda tabs, energy drink tabs and soup tabs. Help us collect Kisses for Aly and donate them to your local Ronald McDonald House. Or make a monetary donation to them as well," the post read. 

FOX News contributed to this report. This story was reported from Los Angeles.