A two-year-old boy has died after falling from his father’s arms while on an escalator at a mall in Aurora, Colorado.

CBS Denver reports the incident happened around 4:30 p.m. on Sunday at the Aurora Town Center. Police said the toddler’s father was carrying him when the boy slipped out of his arms, falling over the railing and onto the first floor below. Witnesses said they saw the small boy lying on the ground unconscious afterward.

The boy was rushed to the hospital with life-threatening injuries and died early Monday morning. 

“I was in one of the shoe stores and I heard a lot of screaming, I heard a lady screaming, then out of nowhere the shop owner ran outside he was on the phone I heard him saying, that something happened, and he couldn’t close the store because he had guests. And then he looked at me, he told me what happened that a little kid fell off the escalator,” witness Cesar Solorzano told CBS Denver.

Although the incident is believed to have been a tragic accident, authorities say it is currently still under investigation.

“All incidents where a child of this age is seriously injured or killed are thoroughly investigated by our Crimes Against Children (CAC) Unit,” Aurora Police Department spokesperson Matthew Longshore told reporters Sunday. “The investigation remains open and active. We are asking anyone that may have witnessed this, that have not yet spoken to the police, to please reach out to Metro Denver Crime Stoppers so that we may follow up with them.”