A four-year-old boy, who was left alone in a hot SUV for almost three hours, reportedly had a core body temperature of 110 degrees when he was found, an arrest warrant affidavit for his mother has stated.

The boy, Kaysen Neyland, 4, was rushed to the hospital later last month, however, he was later pronounced dead.

Kaysen's mother, identified as 38-year-old Lisa Neyland, was arrested on Tuesday in connection to her son's death. She now faces a felony charge of injury to a child, according to New West9.

Kaysen was found unresponsive inside an SUV parked in the driveway of his family's Providence Village home, nearly 10 miles east of Denton, on June 20.

According to police, he was airlifted to Children's Medical Center Dallas where he died from "heat-related injuries" two days later.

Officials soon issued an arrest warrant for the boy's mother for gross negligence.

The warrant revealed that the 4-year-old was left in the SUV for hours before his 11-year-old brother found him.

The mother reportedly told authorities that she believed that the child had only been inside the vehicle for just 30 minutes.

Reports state that Lisa, a mother of four, had taken her 11-year-old son, his friend, Kaysen and his twin brother to a convenience store that day to buy candy.

The 11-year-old told police that he was sitting in the backseat between his two brothers' car seats.

The affidavit states that, when the family reached home, the boy unbuckled Kaysen's and his other brother's car seats.

He then lifted his other four-year-old brother out of the vehicle and told his mother to grab Kaysen.

The 11-year-old told officials that he went inside the house with his second twin and friend, assuming that his mother had taken Kaysen out of the vehicle. 

Lisa, however, told police that she assumed all the children were inside the house with her but she never checked to be sure.

According to the warrant, when Kaysen was discovered, his eyes were open but he was unresponsive when paramedics arrived.

Reports state that the SUV was parked in direct sunlight on a day that reached the mid-90s.

The warrant added that an autopsy conducted on the child revealed that he died from "hyperthermia due to prolonged exposure to extreme heat."

Authorities said that after an "exhaustive investigation", they subsequently arrested the mother on a second-degree felony charge. She is currently being held in the Denton County jail in on a bond of  $75,000. 

Aubrey police Chief Charles Kreidler, in a statement, wrote: "This tragic situation happens too often in Texas and across the country," adding that at least 16 children across the country have died of heat stroke after being left in hot cars this year.