Story highlights A 3-year-old boy dies after being wrapped in a blanket

It was a form of discipline his caretakers called "the wrap"

The adults looking after the boy are charged with aggravated manslaughter of a child

To discipline a 3-year-old boy, three caretakers would wrap him tightly in a blanket and tie the ends to constrain him.

The child was wrapped up in that manner when he suffered a "horrible death," police said.

Now, the two Florida women and one man who were watching Michael Lee McMullen are in county jail and charged with aggravated manslaughter of a child.

The Lee County, Florida, sheriff's office said it received a call last Saturday about an unresponsive child. Young Michael was transported to a hospital but was pronounced dead within the hour.

The boy was in the care of Donella Trainor, 45; Douglas Garrigus, 21; and the child's grandmother, Gale Watkins, 56, authorities said.

They gave deputies a rudimentary and incomplete version of events, according to the sheriff's office.

The trio told deputies that Michael was having behavioral issues and was put down for a nap. When Trainor went to wake him, she found him covered in sweat and unresponsive.

Follow up talks with the three adults on Tuesday led to their arrests and charges.

Among the details that emerged was that Trainor used a discipline method she called "the wrap," which authorities described as "willful torture (and) malicious punishment."

"She would literally roll a child in a blanket and tie the ends down so as to prevent movement or escape," the sheriff's office said in a news release.

"In my experience, this is not something we see every day," sheriff's spokesman Sgt. Dave Velez told CNN.

Other children were at the home at the time of the incident, Velez said, but he declined to comment on their current whereabouts.

Watkins is Michael's grandmother, Velez said. The relationship between the boy and the other two adults was not immediately known.

According to the sheriff's office, Trainor did the "wrap" on Saturday, placing the child face-down in a crib as he "screamed and pleaded" to be released.

At separate points, all three caretakers entered the room, often to tell Michael he would be released if he calmed down, authorities said. At one point, Garrigus said he could hear the boy crying and hyperventilating, the sheriff's office said.

When Michael stopped crying, Trainor told deputies, she assumed that he had calmed down and was resting. It was later, when she went to wake him, that she found him "soaking wet" and unresponsive, the sheriff's office said.

In addition to aggravated manslaughter of a child, Trainor is also charged with aggravated abuse of a child.