The baby may have been left in the Bumble Bee Day Care Center van for about four hours before he was found Thursday afternoon, police spokeswoman Anne E. Schwartz said. How the baby died was not immediately known; the temperature in the area was in the 50s at the time.
Schwartz says the van's 44-year-old driver was arrested on a tentative felony charge of leaving a child in a child care vehicle unattended. His name was not immediately released.
The child's grandmother, Remona Williams, told the Milwaukee Journal Sentinel the victim is Jalen Knox-Perkins and he had been attending Bumble Bee for about a month.
Williams also told CBS affiliate WDJT-TV that the baby always sat in the first seat of the van.
She also claims that while the baby was checked in on a list when entering the van, to her knowledge the baby was never checked off for leaving the van and entering the daycare facility.
An autopsy was scheduled for Friday morning.
Erika Monroe-Kane, a spokeswoman for the State Department of Children and Families, said Bumble Bee's owner also owns a preschool, Alphabet Street Learning Center. Both facilities have been shut down while the state investigates.
An Alphabet Street employee there, who was later fired, was charged recently with breaking the arms of two children.
Bumble Bee had been licensed only since March and had some noncompliance issues that were not related to transportation, Monroe-Kane said. Alphabet Street has been licensed since 1990. Monroe-Kane said she only had immediate access to its records for the last two years but said it also had no recent issues regarding transportation of children.
In February, a 48-year-old woman was charged with a felony after she allegedly left a 4-month-old in a closed vehicle in 80-degree weather in July.