Family and friend held a vigil for Isaiah as questions about his death remained unanswered.
On Saturday, the grief-stricken Polk County community learned the 2-year-old boy from Centuria, Wis., had the key to the trunk where he died with him -- but it's still unclear how he got inside.
On Friday, a preliminary autopsy report shows Isaiah Theis died from hyperthermia -- extreme overheating -- after an officer found his body at about 10 p.m. on Wednesday night.
There were no other signs of trauma, bruises or broken bones, but many questions remain unanswered. He had been missing for over 26 hours as searchers meticulously scanned densely wooded areas within two miles of the home. However, the toddler hadn't gotten very far.
The family's pastor family members confirmed the toddler had the key to the vehicle with him in the trunk, along with several other sets of keys. The boy's father ran a business repairing automobiles near the home.
The initial investigation indicated the Chevy Impala, which was being repaired by the boy's father, had been looked into, and the area around the vehicle had been searched several times; however, searchers were told the vehicle had been locked before the toddler went missing and that it was highly unlikely that he was inside.
Polk County investigators still do not know how the toddler got into the trunk after disappearing on Tuesday night while playing with his 7-year-old brother inside their home.
On a hot day, a trunk can heat up to 150 degrees. High temperatures registered in the 90s the day the boy went missing.