Transcript for CPR Saves More Than 92,000 Lives Annually; Only 4 Percent of Americans Train Each Year
And now to the desperate moments for a mother whose baby suddenly stopped breathing, and the chance encounter in that emergency that changed all their lives. Here's Adrienne Bankert. Reporter: Tonight, a frightening lesson on the importance of cpr, playing out in a Florida DMV. Shakira Nelson's 15-month-old son, not breathing. At that moment I was in panic mode. Reporter: Surveillance video shows Hillsborough county sheriff's deputy Steve Donaldson leaping into action. You can see him listening to the baby's chest. I never realized how small babies were until until they are in your arms. Reporter: Donaldson laying the toddler on the ground, administering compressions. In those critical moments before the ambulance could arrive, Corey started to breathe again. I said a little prayer, and I said, god, give me strength to save this baby. Reporter: Thankfully, deputy Donaldson had just retrained in cpr three weeks ago. Cpr saves more than 92,000 individuals annually. But amazingly, only about 3.5% of Americans train in the technique each year. The hero, reunited with Corey and his grateful mom. I look at the video and I say thank god for deputy Donaldson, because without him, my baby wouldn't be here. Reporter: Tom, this was a clear case of right place, right time. Deputy Donaldson wasn't even scheduled to work that day. He was filling in for another officer. It's certainly a shift that he and this family will never forget. Adrienne, thank you.
This transcript has been automatically generated and may not be 100% accurate.