Early on Oct. 6, Erin Piche-Pitts was awakened by the sound of her baby crying. She later told the authorities in Florida that she had picked him up from a bassinet, prepared some formula in a bottle and settled back into bed with him, propping him up with a pillow and nestling his head in the crook of her arm. Then she dozed off.

Two and a half hours later, according to a Polk County sheriff’s affidavit, Ms. Piche-Pitts, 25, woke up “in a panic.” Blood was on her baby boy, Javier, who was less than a month old, and vomit was coming out of his mouth, she told officials.

Ms. Piche-Pitts, of Winter Haven in Central Florida, said she tried to revive the boy, and called 911. He was later pronounced dead at a hospital.

When investigators interviewed Ms. Piche-Pitts about the baby’s death, according to the document, she said, “It happened again.”