I'm a cautious mom who had a hot car scare. Here's my plea to parents and lawmakers.

It was hot day in June 2017 when Erin Holley and her family were in the midst of moving to another home.

Holley, her husband and two children, who were 4 years old and 4 weeks old at the time, were riding in two separate cars to a storage facility. The couple decided to take a break, jump into one car and bring the kids to the park.

"We were so sleep deprived," Holley told "Good Morning America." "Our 4-year-old was still adjusting to having baby brother. We at some point moved both children to one car. It was a blur."

"We drove to the park and when we went to move the bucket car seat to the stroller, we realized he was not in the car," she added. "I couldn’t feel my extremities and I screamed, 'Oh my God, the baby.'"

Holley resides in South Carolina, which had the highest number of heatstroke deaths in 2018, according to KidsAndCars.org.

At a May press conference in front of the U.S. Capitol building in Washington, D.C., Holley detailed her frightening close call when her 4-week-old son was forgotten in a hot car. The purpose of the press event was to promote the Hot Cars Act, which is a bill introduced in 2017 with the support of the Kids and Cars organization.

The Hot Cars Act would direct the Department of Transportation to issue a final rule requiring all new passenger motor vehicles weighing less than 10,000 pounds be equipped with an auditory and visual system alerting the driver to check rear seats after their car is turned off.

Holley is now committed to spreading awareness on hot car accidents, as a parent advocate for Kids and Cars.

Here is Holley's full story and statement she read at the Capitol, printed with her permission.

"I'm here today representing two groups of people affected by hot car deaths and the need for technology to prevent them," Holley read at the conference. "First, I'm one of countless parents who have experienced a near miss and unknowingly left my beloved child in a vehicle."

"When my gorgeous, funny 2-year-old son, Finn, was 4 weeks old, we hadn't slept in basically 4 weeks. We were moving houses which wasn't going well, and we were moving things from one storage unit to another using both cars. We had one child in each car."

Holley continued, describing how she and her husband thought they had consolidated the family all into one car before driving to the park.

However, when she went to put her newborn into the stroller, Holley realized Finn was left in the other car, parked on a lot at noon on a Sunday in South Carolina. It was 88 degrees. The Holleys were about 10 minutes away from the parking lot.

The parents raced back to Finn, beating paramedics they had called en route. When they arrived, the car was thankfully still cool from the shade. Finn was sleeping peacefully, unaware.

Paramedics checked the child's vitals and all was fine, Holley explained.

"But that was when I realized this can happen to anyone," Holley said at the Capitol. "If you had offered me, prior to that day, optional technology (in a car seat for example) to prevent it, I would have emphatically declined and told you I was incapable of leaving my baby in a hot car. I am a cautious, loving, aware mother of two."

A secret is kept, for now.

Holley told "GMA" that she and her husband hugged, prayed and opted not to tell anyone of the incident.

"We were never going to tell a living soul that this had happened to us. It's so shameful," Holley recalled.

The Holleys kept their experience to themselves. But months later, a baby in Finn's day care class, born the same week as Finn, died in a hot car.

It was April 3 and it was tax season. "The child's father, an accountant, drove to work that morning without remembering to stop at the day care," Holley shared at the Capitol, adding that the mother came to pick her son up later that day and learned he had never been dropped off.

The day care director drove the mother to the hospital to meet her husband and hold her baby for the last time.

"While I don't know their family personally, I grieved with the teachers as if we all had lost a baby," Holley said. "For months."

Holley said she grieved with day care staff and was painfully reminded of her own close call when Finn was left in a hot car. Soon after, she learned of another hot car fatality in her community.

"The dad, severely sleep deprived, forgot he had picked up the baby early to spend the afternoon playing together and went home to take a nap," Holley noted. "The baby died in their car in their driveway just a few feet from a father [who] would have traded anything to save his son's life."

After these heartbreaking incidents, paired with her own hot car scare, Holley decided to reach out and join Kids and Cars' mission to help prevent hot car tragedies.

Have layers of protection, until lawmakers make a move.

Holley told "GMA" she and her husband employ multiple safety precautions since their near-miss with Finn, who is now a thriving 2-year-old.

Today the parents do things which forces them to go into the back seat, every day.

"I always put my purse behind the driver seat so it's at the foot of the car seat. I'm absolutely always opening the rear door to get the purse out," she said. "I [also] look in my entire car before I walk away from it," Holley added.

Holley said her husband uses the same method, but with his briefcase.

"A lot of people say, "leave your cell phone in the back." That does not work for me, but I know it works for other families. That’s why I love the left shoe thing, You’re not going anywhere without your left shoe," she explained.

Holley's plea to parents is to do what works for their family.

"Ask or demand" that your child's day care calls your cell phone or job, should your child not arrive on a scheduled drop-off day. In addition, if an extended family member is driving with your child, develop a safety plan with them as well.

"It is one of the cruelest things ever to say to family and friends that you're afraid they might leave a child in the car, but it's also one of the kindest," Holley told "GMA." "It's insulting, but at the same time comes from a place of pure love because it's such an easy vulnerability to overlook."

These hot car deaths were preventable.

"It's not a great philosophical debate. The technology already exists. There's not a huge expense involved," Holley said during her plea to lawmakers at the May press event.

"Every time I open my car door all summer and that wave of hot air hits me, I am overcome with the thought of the babies that might at this very moment, be trapped in a hot vehicle and need our help," she added.

"...and no one can hear them, not even their parents. "My car can tell me my tire pressure or if my battery is dying. But it can't provide a simple alarm to prevent anyone from mistakenly letting a baby or pet be locked inside?"

While Holley advocates for families developing their own layers of protection, she insists that employing new technology requiring the detection of life in vehicles, would be the ultimate solution.

"Heartfelt pleas to family and friends to have a plan in place is not solving this," she told "GMA." "The hope is for lawmakers to have car manufacturers help put an end to this."

In 2017, General Motor's rolled out its Rear Seat Reminder System in some of its cars.

GM's feature uses back door sensors that become activated when either the rear door is opened or closed within 10 minutes of the vehicle being started, or while the vehicle is running. Under these circumstances, when you reach your destination a reminder appears on the dashboard as well as an audible chime notification.

This year, Hyundai rolled out a new technology in the redesigned 2019 Santa Fe SUV that could help prevent parents from leaving a child in the back seat of a hot car.

"The safety system adds ultrasonic motion sensors to detect children left in the rear seat, but only if car doors are locked," according to Consumer Reports.

With the available UVO app, the 2020 Kia Telluride offers a rear occupant alert. If the Telluride is off, sensors will detect if someone is still in the back seat of the vehicle.

"It is not fair that our family got to celebrate Finn's second birthday this week and that Jack's family [from the day care] didn't," Holley said at the Capitol. "All because we were fortunate enough to catch our mental lapse in time."

"And it's not fair that Jack's family acted out of pure love, buckling him into a rear-facing car seat as far from the airbag as they could get him ... that last act of love cost him his life and lost them their precious, happy, round-faced boy."

She went on, "Awareness of hot car deaths is at an all-time high with media coverage and NHTSA ads. We can't do much more to educate people. And I'm proof that we can't convince people that this could happen to them. And yet, hot car deaths are on the rise, setting a record last year."

"I can't bear for 2019 to be another record year and for us still not to have taken this basic step toward protecting these sweet babies' lives. This one is easy, and everyone wins." "

Kids and Cars updates their safety tips for 2019.

While apps and car seat sensors can serve as reminders, Janette Fennell, president and founder of KidsAndCars.org, stresses that parents should have additional layers of protection when trying to prevent hot car-related tragedies.

Here are Kids and Cars' safety tips for caregivers.

Make sure your child is never left alone in a car.

1. Look before you lock: open the back door every time you park your car to ensure no one was left behind.

2. Put your cell phone, wallet, work badge or handbag in the back seat to remind you to open the back door each every time you park.

3. Keep a stuffed animal in your baby's car seat, then, place it on the front seat as a reminder when the baby is in the back seat.

4. Ask your babysitter or day care center to call you if your child hasn't arrived as scheduled.

5. Clearly communicate who is responsible for getting each child out of the vehicle. Miscommunication can lead to everyone thinking someone else removed the child.

Make sure your child cannot get into a parked car.

1. Keep vehicles locked at all times, even especially in the garage or driveway. Ask neighbors and visitors to do the same.

2. Never leave car keys or remote openers within reach of children. Fennell said that it's crucial to keep your child from getting into the car, rather than teaching them how to get out: "Be sure your neighbors can lock their vehicles as well."

3. If a child is missing, immediately check the inside, floorboards, and trunk of all vehicles in the area very carefully.

4. Teach children to honk the horn if they become stuck inside a car.

"What we always say is that if there's a body of water nearby, check that first," Fennell said. "Then carefully check all the passenger compartment of all nearby vehicles in the area and check inside the trunk."