Around 1:30 p.m., her daughter, Rhiannon Lopez, put Aiden down for a nap in Vanderwilt's guesthouse. An hour later, Lopez burst through the back door, shrieking. Then Vanderwilt saw her daughter holding Aiden.
"His head lolled on her arm. He was just completely limp. But even more alarming was his color. It was ashen. Yellow-gray. A horrible, wrong color," she said, sobbing while she tells the story 10 months later.
According to the medical examiner's report, Aiden suffocated. A detective who examined the scene after the baby was found noted that the bumper pad in the left corner of the crib was pushed down against the mattress.
Vanderwilt had given her daughter the bedding set as a shower gift.
"I bought them the whole coordinated, lovely, deadly, shebang," Vanderwilt said. "I honestly thought it was a necessary part of a newborn nursery, and I hate myself for not doing my homework."
The safety commission wouldn't comment on Aiden or Preston's deaths, but said it can be difficult to determine how or why a child died.
A baby could have been sleeping with a sibling, for example, or pillows or extra blankets could have been found in the crib too, the agency said.
Safety advocates said they know cases aren't always clear-cut but they say they worry that obvious dangers are being ignored.
"It's not that I'm denying there were other products involved," Cowles said. "But it was the bumper that the baby had their face up against."
Preston and Aiden's deaths included other products.
The night before he died last April, Preston was placed on a sleep positioner, a product that was supposed to keep babies from rolling onto their stomach. Positioners often have foam bolsters on the sides to keep a baby in place. Preston somehow rolled out of his positioner and landed with his face between the bumper pad and mattress.
In September, the safety commission and the U.S. Food and Drug Administration issued a warning about sleep positioners and urged parents to stop using them, retailers to stop selling them and manufacturers to stop making them.
Preston's death was one of 12 deaths in the past 13 years involving a positioner, according to the safety commission. The commission wouldn't say why it took action against sleep positioners but not bumpers.
When Aiden was found dead, his crib contained stuffed toys, blankets, a small pillow, two towels and the bumpers. Safety experts say a baby's crib should be clear of clutter, but his grandmother said those products were at the opposite end of the crib.
Laura and Kyle Maxwell no longer live in the house where Preston died. Laura never slept there another night. She couldn't bear to walk by his room. The couple, both 27 at the time, sold the four-bedroom home in Alaska and in August moved to an apartment in Fayetteville, Ark.
Their nearly 3-year-old daughter, Emma, prays for Preston every night when she goes to sleep. Laura says she struggles when asked, "How many children do you have?"
Kyle said he knows that when people hear his family's story, they'll think what he would have thought: "That'll never happen to me."
Tribune reporter Patricia Callahan contributed to this report.
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Rhiannon Lopez holds her son Aiden next to the crib where he was later found lifeless last February in Austin, Texas. (Family photo)