Records reveal a 5-year-old boy was left alone inside a vehicle for nearly nine hours before he was found unresponsive and later pronounced dead at a La Joya Independent School District elementary school in August.

The boy’s aunt, Diana Trevino Montelongo, is a teacher at Dr. Americo Paredes Elementary School and has been charged with criminal negligent homicide in connection with her nephew’s death. She remains on administrative leave.

RELATED: Teacher charged with criminal negligent homicide in connection with child death investigation, La Joya ISD police chief says  

According to court documents obtained by Channel 5 News, Montelongo had been responsible for taking the boy to school since the beginning of last school year.

Investigators say Montelongo provided a statement saying the boy was asleep in the backseat the day of the incident on Aug. 25.

READ ALSO: Preliminary autopsy results show boy left inside vehicle at La Joya ISD school died of heat stroke, justice of the peace says  

“She arrived at the school and forgot her nephew was in the back seat of her vehicle,” according to the probable cause affidavit against Montelongo.

Surveillance video shows Montelongo getting out of her vehicle at the school at 7:21 a.m. and entering the school alone, according to the affidavit. At 4:02 p.m., Montelongo is seen on surveillance video going to her vehicle and discovering the boy.

Autopsy results determined the boy’s cause of death to be heat stroke.