CINCINNATI (AP) — Authorities in Cincinnati pledged Thursday to find out what went wrong in the death of a 16-year-old boy they say became trapped by a minivan bench seat in a school parking lot. His body was found about six hours after he first called 911.

Police Chief Eliot Isaac said something went "terribly wrong" in Kyle Plush's death. He said a dispatcher was put on administrative leave and that the actions of all personnel involved will be reviewed. Hamilton County Prosecutor Joe Deters said his office is trying to identify experts to help its own probe with the coroner's office.

The coroner ruled the teen died of asphyxia, from his chest being compressed.

A telephone message was left for his parents Thursday.

"This is a horrific tragedy," Isaac said. "We share in their heartbreak."

The teen first called 911 at about 3:15 p.m. Tuesday saying he was stuck inside a van in "desperate need of help." But he was unable to hear the dispatcher's questions, police said, and a callback to his cellphone after it disconnected went to voicemail. Responding police drove through the area looking for signs of anyone in distress, but saw nothing out of the ordinary in the school complex that has several parking areas.

A Hamilton County sheriff's deputy on traffic duty at the school also checked around, police said.

The teen called 911 again at around 3:35. Police said this time he provided a description of the vehicle as he desperately pleaded for help, but couldn't hear the dispatcher. Isaac said the information didn't get relayed to officers at the scene.

"This is not a joke," the teen said over 911." I'm almost dead."

He asked the dispatcher to "tell my mom I love her if I die."

Police were unable to locate him on any of several parking lots of the Seven Hills School complex. A Hamilton County sheriff's deputy on traffic duty as school let out also checked around, police said.

Police said a friend called Plush's parents that evening saying he hadn't shown up as planned for a tennis match. His mother used an app to locate his phone at Seven Hills. They called the county dispatch center, and police said family members then arrived at the unlocked vehicle with the unresponsive teen inside. Police and fire responders getting there just before 9 p.m. were unable to revive him.

The Seven Hills School sent out a message saying Plush had been a Seven Hills student since sixth grade.

"He was a young man of keen intelligence, good humor and great courage, and this whole community feels this loss very deeply," the school said.

"He was truly a spectacular person," classmate Preston Luniewski told WLWT-TV. "He just lit up the classroom."

Authorities indicated he was in the rear of the minivan when he became trapped by a seat.

A Honda spokesman identified the vehicle as a 2004 Honda Odyssey and said there had been no seat-related recalls for that model.

"Our hearts go out to the victim's family during this difficult time," spokesman Chris Martin said. "Honda does not have any specific information from which to definitively determine what occurred in this incident."

Isaac said police will also study possible police equipment malfunctions.

Mayor John Cranley urged prayers for the Plush family, "saying our hearts are heavy."

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