Muskogee police said they don't believe there is any ill intent in this case and it will be up to the district attorney's office if any arrests are made.
Muskogee Police said a woman went to work Wednesday morning and in the afternoon went to a daycare center owned by Eastar Health System to pick up her nephew.
But he wasn't inside the daycare.
"As soon as she realized the child wasn't at the daycare she went out to the vehicle and they called 911 at that time," said Officer Lincoln Anderson.
Anderson said the 6-week-old was pronounced dead.
The hospital released a statement, that stated: "Our hearts and prayers go out to everyone concerned with the incident."
Anderson said it's important for parents and guardians to remember that on average, the inside of a car will get about 40 degrees hotter than the outside temperature.
Lincoln said the incident is rare for Muskogee.
"This is the first one I can remember this year, and I don't even remember having an infant death in a car last year," he said.
And he said one death this year, is one too many.
"Always check your backseat. Just always check your backseat," Lincoln said. "Check your backseat when you go to get in your car, check your backseat when you get out of the car. Before you even lock it."
Police suggest parents put their purses or wallets in the back seat of their car as a reminder to check the back seat before getting out.