*Warning: graphic, disturbing video included.

Local police authorities in Chongqing, China are baffled as to what provoked a 10 year old schoolgirl to maul a defenseless 18 month old baby boy inside an elevator, and then throw him off from the balcony at the building's 25th balcony.

The baby boy, identified as Li Xinyuan, was with his mother inside the elevator. When the doors opened, the mother struggled with the little boy's green bike. It was already too late when she noticed her toddler son did not follow her out of the elevator and was left behind still inside it.

The incident happened at 4:10 p.m. on Nov. 25 in a residential building in the Changshou District.

CCTV footage collected from inside the Chongqing apartment complex lift showed it was a matter of seconds when a schoolgirl, with long black hair and wearing a backpack and a light-blue jacket and pink neck scarf, boarded the elevator just as little Li Xinyuan's mother left it. The schoolgirl saw Li Xinyuan, visibly distressed over his separation from his mother.

The schoolgirl presumably tried to pacify and coo the toddler. What happened next was unthinkable.

The girl then slammed the toddler into the ground. She also kicked and stomped on him more than one time. Upon reaching the 25th floor, she dragged little Li Xinyuan out and then threw him roughly to the ground.

The mother meantime raced in panic to the 25th floor since she saw the elevator lights going up. When she arrived there, she encountered the schoolgirl who told her that her son had been taken by a boy. After sometime, she said it was a girl who took the toddler.

Next thing the mother knew, little Li Xinyuan was later found on the ground outside the building, unconscious and covered in blood.

Li Shuyong, Li Xinyuan's father, said they have received 58,000 yuan ($9,500) from the girl's father. He said it's not enough to pay for medical expenses.

"It costs 4,000 yuan a day and my son has been under observation for 10 days," Li Shuyong said. "Doctors said the operation will cost over 30,000 yuan."

Dan Xingming, the family's lawyer, will demand 300,000 yuan from the girl's parents, adding a local court has accepted the case.

"I can't help crying," a mother wrote on Sina Weibo microblog, "How can a little girl be so twisted as to torture a toddler?"

Apparently, the schoolgirl herself was accustomed to getting beaten by her own parents.

In a report by Beijing News, the girl's father denied allegations his daughter threw out the toddler on purpose. He said hurting the toddler was just her way of "expressing her feelings".

"[By beating the boy] she just wanted him to smile to her and to be friendly to her," the father was quoted as saying.

He then admitted that the girl's parents often beat and scold her.

Video Source: Youtube/ That's Online