(KRON) -- A San Jose teenager has been charged with murder and child sexual assault after his 2-year-old foster brother was found unresponsive on Easter Sunday with suspicious traumatic injuries, according to the Santa Clara County District Attorney’s Office. The toddler, identified by prosecutors as Baby Jaxon, succumbed to his injuries on April 9 after days on life support. The San Jose Police Department and medical personnel found Baby Jaxon bruised and battered in his crib in the early afternoon of April 5 at a residence in the 300 block of Otono Court. Investigators said the boy had been placed into the foster family home in February, and since that time, he had been the victim of repeated sexual and physical assaults. Detectives arrested Baby Jaxon’s 17-year-old foster brother as the primary suspect on April 8. On Monday, the DA’s office filed charges of murder and child assault causing death against the suspect, who has since turned 18 years old. He had previously been charged in the case with multiple counts of sexual assault, including forced sodomy. Trial begins for ‘Girl in the Box’ kidnapper in San Mateo County courthouse Detectives investigating the homicide learned that Baby Jaxon was “placed with a foster caregiver who had a concerning criminal history,” SJPD said. According to authorities, the caregiver was not cooperative or forthcoming in the initial investigation. The teenage suspect was charged in juvenile court due to his age at the time of the alleged murder. Prosecutors said they are seeking to transfer the case to adult court. “If his petition is found true in juvenile court, he could face seven years in Secure Track, a locked facility for juveniles who have been adjudicated of serious crimes,” the DA’s office wrote. “If the case is sent to adult court by a judge, he could face many years in prison.” A full autopsy of Baby Jaxon is pending, prosecutors said Monday. ...read more read less