An early morning wake-up call from a dog turned into a heroic act when a family followed Axel, an adopted border collie, to find 17-year-old son Gabriel having a stroke.

The boy, Gabriel Silva, and his mother, Amanda Tanner, sat down with "Good Morning America" for an exclusive, on-camera interview about the harrowing experience and miraculous act.

The incident began when Silva collapsed on the way back to his room in the middle of the night.

"On the way back to the room, I just, like, I fell," said Silva.

Silva described the sensation as feeling like the room was "caving around me."

Silva, who had taken senior photos at school earlier in the day, was almost non-verbal during the incident.

As Silva struggled, Axel darted into the room where Tanner and her husband were sleeping.

"I thought you know, he's waking me up at five in the morning. Not good timing, but he just needed to go outside to use the restroom," said Tanner.

When Axel refused to leave the room, Tanner's husband, Daines, followed him to Silva's room.

Upon discovering Silva, the family rushed him to Memorial Hermann Hospital in Texas, where he was diagnosed with an ischemic stroke.

"There was a blood vessel in his brain that had closed off partially," said Dr. Sabih Effendi, MD Stroke Medical Director at the hospital.

"It was a dissection of the artery that was causing a narrowing of it to not get blood to the brain."

According to the CDC, each year nearly 800,000 people in the U.S. have a stroke. While risk increases with age, about 15% of strokes happen in children and adults under the age of 40.

Up to 25% of strokes in young and middle-aged people are due to artery dissections, as in Silva's case. This dissection can lead to formation of a blood clot that then can block blood flow, and therefore oxygen, to parts of the brain.

Silva said the incident gave him a new perspective on life. He said he's learned not to "dwell" on things that may make him sad.

Tanner expressed appreciation for Axel and his life-saving efforts.

"I am beyond grateful for whatever sensitivity Axel has to tell us what's going on and to have moved that so fast."