NORTH POTOMAC, Md., (WUSA9) -- "Loved to run and jump and climb and laugh, just never a dull moment," says Erica Thomas.

Cormac Fitzgpatrick Thomas was athletic and filled to the top with discovery. At two and half years old, he had an appetite for adventure, wherever he could find it.

Mac's parents marveled at his curious mind. He even figured out how to undo the childproof knobs inside their North Bethesda home.

"We took a lot of his wall hangings off the walls. We tested out what his kind of reach was and only kept the things he couldn't quite get to," says his mom Erica Thomas.

"We thought, you know, long and hard about all the potential scenario's that could create danger in household," his dad Stephen says.

Erica and Stephen Thomas knew part of that danger involved the cords in window blinds.

"I decided to put the cords on to the outer side of the window so that it would not be reachable from the bed, that was my biggest concern," Erica says.

They didn't realize there was another danger behind the Roman blinds they bought for their toddler's room. On the morning of March 1st, Erica was eager to start the day with her two sons. Stephen, a doctor in the U.S. Army, was returning home from a three month deployment. Erica hadn't heard a peep from Mac all morning, so she went to his room to wake him up.

"I went in and he was lying underneath the window with his beloved monkey and bear and I thought, oh he's just sleeping," she says.

As she got closer, she realized Mac was not breathing. She called 911, started CPR and eventually looked up at the window.

Erica says, "I saw that there was a string coming from out behind the blind I could see, and it just kinda clicked in my head at that moment, oh my God."

CPSC Window Covering Information Center

Mac is one of four children who've died in corded blinds in just three weeks. The nonprofit Parents for Window Blind Safety says in at least two of those incidents the blinds were equipped with safety kits that are supposed to keep this from happening. Linda Kaiser started the advocacy group after she lost her daughter 12 years ago.

"I think the misconception is that if you have a retrofit kit or safety kit attached to the product that it is strangulation free, and that is simply not the case," Kaiser says.

When blinds hit the market they are supposed to have safety built into the design. That includes eliminating the loop on the outer cord and having a stop in place that would keep an inner loop from forming. But this is a voluntary standard not a mandatory one. And with each tragic story, it's a reminder that even these safety precautions won't save all children.

U.S. Consumer Product Safety Commission spokesperson Kim Dulic says, "There are cordless window coverings on store shelves. There are window coverings with inaccessible cords. We're working really hard to get the message out there that these are the safest options for young children."

Window Covering Safety Council

As they look back, Erica and Stephen Thomas wish they'd known all the potential issues with cords, and the safer alternatives on the market. They say their tragedy is proof this can happen to anyone.

"The odds are millions to one, but we're the one. And there's a whole bunch of other families that are the one," says Stephen.

We can't bring Mac back, but maybe somebody else gets to keep their baby home and safe with them," Erica says.