LAS VEGAS (KLAS) — The boyfriend of the mother of a one-year-old boy allegedly abused the child, resulting in his death in a case a doctor described as one of the most severe he had ever witnessed, the 8 News Now Investigators have learned.

Christian Moniz Rabino, 28, faces charges of first-degree murder and child abuse for the death of Kai Tesoro who was 17 months old at the time of his death. Police identified Moniz Rabino as Kai’s mother’s boyfriend.

On June 1, Metro police received a call about a child, later identified as Kai, who was not breathing. Paramedics transported Kai to a hospital where doctors noted he “had bruising to his head and a fracture to his right leg.” The child’s mother told police Kai fell off a bed a few days prior and bumped his head.

Doctors later determined Kai had several brain bleeds and a fractured leg, possibly “caused by a large amount of force,” documents said. A doctor also noted Kai suffered “non-accidental trauma” to his eyes from suspected shaking and noted the alleged abuse “was one of the worst cases he had seen,” documents said.

Doctors at the hospital believed the fatal injuries occurred the day Kai was taken to the hospital and that he suffered “a massive stroke,” documents said.

Doctors took Kai off life support, and he died at the hospital on June 6, documents said. Kai previously had a seizure in February and was evaluated at a different hospital.

Moniz Rabino told police Kai “had not been feeling well for the past few days and had a fever,” documents said. The boyfriend said he bathed the child and said Kai then stopped breathing.

A witness told police Moniz Rabino allegedly injured Kai’s mother and bruised her, documents said. The witness also said Kai’s mother lied about Kai falling off the bed to protect herself and that Moniz Rabino allegedly convinced Kai’s mother not to take the child to the hospital.

Kai’s mother later told police she witnessed Moniz Rabino allegedly shake the child before and abuse him. Specifically, police suspect “[Moniz Rabino] became frustrated with [Kai’s] inability to walk on his own and [slammed Kai’s] feet first on the floor,” documents said.

Last week, Las Vegas Justice Court Judge Eric Goodman declined to set bail. A preliminary hearing was scheduled for Aug. 7.

Kai’s family donated his organs to help other children, his grandfather, Steve Teroso, said.

“Kai is a true hero; his Aloha and spirit will continue to live on,” his grandfather wrote on a GoFundMe page. “Kai was a joyful and spirited child who brought immense happiness to everyone who knew him, bringing instant smiles to those he met. All he ever wanted was love. He will forever be his daddy’s ‘Fat Boii.'”

The Tesoro family was raising money on GoFundMe for funeral expenses and to help raise money for therapy and education for Kai’s 3-year-old sister.

For a list of local and state resources for domestic violence and abuse victims, visit this link.