Update, 11:55 a.m. Thursday:

Eight-month-old Raylee Mercer died of suspected hyperthermia after being left alone in a parked car for 2½ hours, according to preliminary autopsy results, said Dr. William “Beau” Clark, the East Baton Rouge Parish coroner.

Clark said the death appears accidental but said additional tests are still pending.

Original story:

Baton Rouge police arrested the father of an 8-month-old girl who died Wednesday after he forgot she was with him and left her inside a hot, parked car.

Marvin Mercer, 31, drove to work Wednesday morning to Madison Preparatory Academy but didn’t realize until 2½ hours later that his baby daughter, Raylee Mercer, was still strapped in her car seat in the backseat of the car, said Sgt. Don Coppola Jr., a Baton Rouge police spokesman. The vehicle’s windows were rolled up and the doors closed.

Mercer told detectives Wednesday afternoon that he was supposed to drop his daughter off at a day care but forgot, instead following his normal daily routine, going to work at Madison Prep about 9 a.m., according to a Baton Rouge police report.

He’s the head baseball coach at the charter school.

When he returned to his car during his lunch break about 11:30 a.m., Mercer told detectives, he heard a coughing noise from the backseat and saw fluid dripping from the baby’s nose.

Mercer drove her to Baton Rouge General-Mid City, where medical staff attempted to revive the baby but to no avail, the report says.

The police and Dr. William “Beau” Clark, the East Baton Rouge Parish coroner, have not yet confirmed how the baby died. An autopsy is scheduled for Thursday, Clark said.

Mercer, 13675 Jackson Road, Zachary, was booked into East Baton Rouge Parish Prison on a count of negligent homicide, Coppola said. Mercer was released on a $10,000 bond late Wednesday.

A colleague at the school spoke highly of Mercer on Wednesday.

“He is a dedicated teacher and coach,” said Dujan Johnson, the CEO of Community School for Apprenticeship Learning, the organization that oversees Madison Prep.

“He is also a devoted family man, whose wife and children were always present at school events,” Johnson said.

The long driveway and large front lawn of the Mercer’s home was full of cars Wednesday evening, with more arriving as family members and friends came to offer support. While some family members talked outside, others were in the living room as the story of the tragedy played on the television screen.

A child’s playpen sat in the corner and the television was framed by bookcases filled with family photos of a happy couple, who were married in 2014, and their family.

A framed piece of art on an end table by the front door reads “May all who enter as guests leave as friends,” and a wedding photo of a beautiful bride sits in the dining room.

The family members gathered at the home said the family is grieving and no one wanted to comment at this time.

If Raylee’s death was caused by being stuck in a hot vehicle, hers would be the 11th such death in the U.S. this year, and the first in Louisiana this year, said Jan Null, a research meteorologist at San Jose State University. He said he began studying this problem after he found no one else was tracking it.

Last year, Louisiana’s only child vehicular heatstroke death was also in Baton Rouge, Null said, when 22-month-old Angel Green perished in a sweltering day care van at 6345 Prescott Road on June 5, 2015.

Two women were arrested in that case, with one of them booked on a count of negligent homicide.

The temperature in Baton Rouge reached 89 degrees at noon Wednesday, with a high of 93 degrees, according to the National Weather Service.

Null said that when the air temperature is about 91 degrees outside, the interior of a vehicle can grow hotter than 135 degrees.

Last year, the deaths of 24 children in the U.S. were tied to being left in hot automobiles, down from a spike of 49 deaths in 2010, according to Null’s data.

From 1998 through 2014, a total of 636 infants and children died of heatstroke inside hot motor vehicles. Just over half, 338, were accidently forgotten by a parent or other caregiver, with 98 being the mother and 115 the father.

Raylee would be the 22nd child to die of vehicular heatstroke in Louisiana between 1998 and Wednesday, out of 672 nationwide during that time span, according to Null’s data. In addition to accidental deaths, that number reflects children who were playing in vehicles or those who were intentionally left inside a vehicle and died from heatstroke.

Advocate staff writer Amy Wold contributed to this report.