The gut-wrenching truth behind the death of a 3-year-old boy who fell from a high-rise in Missouri has been revealed by officials.

The toddler – Tarvis Phenix III – died when his father Tarvis T. Phenix Jr. was taking care of him while his mother recovered from a leg amputation.

The 26-year-old father initially said he momentarily stepped out from his 11th-floor apartment at Parkview Apartments in St. Louis to smoke on April 9.

However, surveillance video captured Phenix that night around 11.50pm driving away from the building, according to a probable cause statement cited by the St. Louis Dispatch.

The boy, who went by T3, was seen on video roughly 45 minutes later on April 10, leaving the apartment and wandering around the 11th floor, read the statement.

T3 was then seen around 12.45am climbing a bench which was below a window ledge before falling to his death.

His father returned 10 minutes later and reported his son missing, said officials.

Terance Hardy, a relative of the boy, told KSDK, prior to the new allegations: ‘He [Phenix] went down the hall searching, knocking on people's doors. He couldn't find him, and that's when they originally thought he was missing.'

Officers then arrived at the building in response to a missing child report, where they discovered the boy's body outside the building.

A complaint in the case alleged that Phenix knowingly acted in a manner that created a risk for the boy, which resulted in his death, according to the Dispatch.

Hardy noted in a GoFundMe fundraiser that T3's mother, Diamond Hamilton, was staying with his father's family as she was in rehab recovering from having her leg amputated. He noted that the leg was amputated as a result of gun violence.  

'For the past 2-3 years, she has been in and out of rehabilitation,' Hardy, Hamilton's cousin, wrote.

'She is currently in rehab dealing with mental [and] emotional stress, and this has made her situation even worse!'

During her recovery, T3's father's family had stepped in to help look after him, Hardy explained.

He said she has two other children to take care of as well.

At the time of this report, more than $9,500 had been raised to help her during this difficult time.

The grieving mother has taken to Facebook to share her painful loss, writing: 'I prayed I prayed I prayed and asked god every night too [sic] protect my kids for me If I was away from y'all.'

Family members gathered for a balloon release outside the apartment building on April 12 in memory of T3.

A crowd gathered outside, holding blue balloons for him.

'Just a vibrant little thing. I just want people to remember most how intelligent he was for a 3-year-old,' Hardy said. 'Just a ball of life.'

Phenix is being held without bond in connection with the incident.