The 2-year-old Wisconsin boy found locked in a trunk last week likely died soon after his family notified authorities he was missing, according to a statement from the medical examiner Tuesday.

Isaiah Theis’ mother told sheriff’s deputies that her son was last seen around 7:30 p.m. July 16 while playing with his brother at their home in Centuria, Wis. Isaiah’s family and friends searched for him and then notified the Polk County Sheriff’s Office about 8:50 p.m. when they couldn’t find him.

“It is most likely that Isaiah was deceased, or had experienced irreversible damage, by 9 p.m. if he was already in the trunk around the time it was reportedly realized he was missing,” Dr. A. Quinn Strobl of the Midwest Medical Examiner’s Office in Anoka County, who performed the autopsy, said in a statement.

Isaiah was found the night of July 17, a little more than 24 hours after he was reported missing, in the trunk of a car that his father was repairing near their home. The boy had the keys with him in the trunk, the Polk County Sheriff’s Office confirmed Tuesday. The family’s pastor has said it was likely that Isaiah climbed into the car by himself.

Preliminary autopsy results revealed Isaiah died from excessive heat. Temperatures rose to 91 degrees July 16 and 92 on July 17 in Centuria. The temperature inside the trunk would have been much higher.

“Individual cases of children who are left in sealed, non-air-conditioned cars for a known period of time document how quickly, within a matter of hours, death can occur,” the medical examiner said.

More than 2,400 volunteer searchers poured into the area to help look for Isaiah. Searchers had looked in the vehicle and in the area around it several times but hadn’t checked its trunk. They had been told that the vehicle had been locked before the boy wandered off and that it was extremely unlikely that he could have been in it.

Services for the boy will be on Wednesday, with visitation starting at 10 a.m. at Alliance Church of the Valley at 1259 State Road 35 in St. Croix Falls. The funeral will be at 11 a.m. with a private burial for family members.