A Mayo Clinic nurse, Alyssa Yoder, has been volunteering for years at the 26.2 with Donna Marathon to warn and lookout for others.

"I've worked the main medical tent, I've worked some of the first aid stations, and this year I'll be working the main medical van," said Yoder.

Why she shows up every year to volunteer dates back two years ago-- to her birthday weekend, April 13, 2014. Yoder, her younger brother Jason, and his wife were participating in a marathon in Raleigh, North Carolina.

"Jason was much faster than I was so he decided to run so he was in the front corrals. I decided to walk so I was in one of the back corrals," said Yoder.

The trio took off, Yoder says the route was beautiful with blue skies and loud music. But in an instant, it all changed.

"We got a call from the marathon director that Jason had had an emergency around mile 12," Yoder said.

Jason had collapsed. He was rushed to the hospital.

"They had done everything they could but that Jason had passed on the marathon course," said Yoder.

A cardiac arrhythmia-- or sudden cardiac arrest-- was the cause according to doctors. A complete shock to the family.

"He had always been healthy some full marathons, long term cycling events," Yoder said. "It wasn't something that we thought about. He was just very healthy."

Since her brothers death, Yoder has dedicated herself to being there for other runners in need... Advocating for Automated External Defibrillators to be well stocked at marathons all over the country-- including the 26.2 with Donna.

AED's detect abnormal heart rhythms in the victim, and will administer a shock... only if necessary. Proponents say the technology could save 40-thousands lives every year.

"If an AED would've been close or trained bystanders were there, you always wonder if the outcome could've been different," Yoder siad.