There were no obvious signs of foul play, but it has not been ruled out, said Diane Richardson, a spokeswoman with the Charles County Sheriff's Office.
Richardson said authorities are trying to trace the 24-year-old woman's movements over the past several days "to find out what was going on in her life, what led to this moment."
Sheriff's deputies went to the park in La Plata, Maryland, about 7 a.m. after being called to check on the welfare of the woman and child, Richardson said. The officers went to remove the boy from the swing and give him first aid, but "it was instantaneously clear the child was dead," she said. There were no signs of trauma to his body.
Deputies cut the chain on the swing's seat and removed the body, which was taken to the Officer of the Chief Medical Examiner in Baltimore. The woman was able to answer some of the deputies' questions before being taken to a local hospital for a medical evaluation, Richardson said.
The mother, whom police did not identify, listed several addresses, including one in Washington and another in Charles County, where La Plata is located, Richardson said. She said the woman also had stayed with a relative in the county.
La Plata is about 30 miles southeast of Washington, with a population of about 8,700, according to the town's website.
"It's a very sad and tragic situation for the mother, her family, the officers," Richardson said. "All of us want answers. We're working very hard on that."
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