Hours before Gannon Stauch was reported missing in January, his stepmother allegedly killed the 11-year-old in his bedroom before stuffing his body in a car at their Colorado Springs home, according to a newly unsealed arrest affidavit.

While authorities frantically searched for the boy the morning after his disappearance was reported, Letecia Stauch dumped the 5th grader’s body off a highway, the document states, which was first reported by CBS Denver.

“Physical evidence recovered from the residence and inside Gannon’s bedroom supports that a violent event occurred in the bedroom,” the El Paso County Sheriff’s Office arrest affidavit says, adding that “blood spatter” was found on the walls, a mattress, and carpet.

Stauch, 38, was charged in March in connection with the 11-year-old’s murder, five weeks after reporting him missing and setting off a massive search effort by federal and local authorities.

The arrest affidavit from Feb. 28 provides new details about Gannon’s case, including that Stauch’s story “dramatically changed multiple times” from her original statement that the boy never returned from a visit to a friend’s house.

“Letecia lied to investigators on multiple occasions, has unexplained abnormal behavior such as obtaining a rental car, disconnecting her cellphone from the cellular network for an extended period of time, the false reporting of alleged rape, abnormal patterns of travel, a continuously evolving story with material changes in facts and circumstances, and has since left the State of Colorado,” the affidavit states.

The stepmother was arrested in South Carolina on March 2 and faces 13 charges, including first-degree murder, child abuse resulting in death, tampering with a body, and tampering with physical evidence. About two weeks after her arrest, the boy’s remains were found in a suitcase under a Florida overpass—nearly 1,400 miles from his home. It’s unclear how his body got there.

According to the 32-page affidavit, Stauch reported Gannon missing on Jan. 27 at 6:55 p.m., stating the 11-year-old “was supposed to be home approximately 1 hour ago, and that she was unable to locate him at his friend’s house.”

The fifth-grader did not attend his elementary school that day, and Stauch allegedly told her employer she would not be able to go into work because her “stepfather was killed after being hit by a car.”

According to the affidavit, authorities believe that at least three hours before Stauch called authorities, she murdered Gannon and moved his body to the garage, where she loaded him into the back of her Volkswagen Tiguan. Stauch then allegedly cleaned up the evidence and alerted the sheriff’s office.

When deputies arrived at the Colorado Springs home, they “conducted a limited search of the residence” and took a statement from Stauch, who was “Gannon’s only known adult supervision in the days preceding and on the day of his murder,” the affidavit states. Gannon’s father, a member of the National Guard, was out of town on duty at the time, the sheriff said.

The affidavit states that Gannon’s body remained in his stepmother’s car until the next evening when investigators believe Stauch dumped him in an area off of Colorado Highway 105. The Metro Crime Lab later determined the “blood discovered in Gannon’s bedroom, the Stauch’s garage, and the blood on a piece of particle board” off the highway “all matched his DNA profile.”

Investigators said the 38-year-old Stauch later changed her story, claiming she’d been held at gunpoint and raped by a man who had abducted Gannon in a Jan. 29 interview, according to the affidavit. She stated that during the abduction, she “had hit her head and may have blacked out”—though detectives did not see any notable injuries on her.

“The interviewing Detectives believed her statements were false based on prior experience investigating sexual assault cases,” the affidavit states, noting that her other statements were “blatant lies designed to mislead investigators.”

In the days after the 11-year-old’s disappearance, Stauch publicly defended her innocence in an interview with KKTV-11, stating she would “never ever hurt his child.”

While Stauch said she could not go into details about the case, she told the news outlet that the day the 11-year-old went missing, the two went for a hike at Garden of the Gods. “The rumors have gotten so bad,” she said. “I’m like, ‘Why are you saying Gannon is dead?’ He is not dead. We are gonna find Gannon.”

Stauch was arrested a month later in Myrtle Beach, South Carolina.