Police are still trying to determine why one California mother tried to kill her daughter by crashing their vehicle into a semi truck.

Witnesses were surprised when they realized the driver of an SUV that had crashed into a truck was beating her young daughter in the vehicle after the crash.

Stephanie Irene Aguilar, 31, of Rancho Cucamonga reportedly crashed her GMC Yukon into the semi while traveling west on California’s 10 Freeway in Monclair. After the incident, as witnesses called 911, they saw Aguilar punching her young passenger before slamming her head into the vehicle’s center consol.

While on the phone with emergency personnel, the horrified witnesses were relaying the odd account. While some stayed on the phone, others grabbed Aguilar and kept her away from the girl, later identified as her 8-year-old daughter.

When California Highway Patrol arrived, Aguilar was reportedly agitated and attacked an officer, injuring his arms.

Unsure of her physical condition, Aguilar, a respiratory therapist, was taken to Colton’s Arrowhead Regional Medical Center. She was released the following day and immediately arrested.

The daughter is said to have suffered only minor injuries.

Aguilar was arrested on suspicion of attempted murder, corporal injury on a child, and obstructing a police officer. She is being held in lieu of $1 million bail at West Valley Detention Center and was scheduled for arraignment on Monday in West Valley Superior Court.