A 10-year-old boy was charged with first-degree murder in the death of his seven-month-old niece, who was shot in the head inside a home in the city of St. Louis, Missouri, judicial authorities reported.

According to case documents reviewed by ABC News, the minor took a firearm that was hidden under a mattress and shot the baby. Another seven-year-old child was also in the home at the time of the incident.

Officers from the St. Louis Metropolitan Police Department went to the property on Friday after receiving a call alerting about a shooting. The baby was rushed to a hospital, where she died despite medical efforts to save her life.

Baby's father also charged

After the investigation, detectives concluded that the alleged shooter was the 10-year-old boy, who was taken into custody of the authorities.

The minor's father, identified as Ca'Marion Pawnell, 19, was later arrested.

The prosecution charged him with second-degree murder and several crimes for endangering minors.

According to court documents, prosecutors maintain that Pawnell allowed the firearm to remain within reach of the children who were in the home, which led to the death of his daughter.

During the interrogations, the young man would have acknowledged that the weapon belonged to him and that he kept it under the mattress.

The minor will remain in the juvenile jurisdiction

Authorities noted that the boy stated that he knew where the gun was located and admitted that he had had access to it for an extended period of time, including handling it on previous occasions.

The juvenile was taken into the custody of the Missouri Children's Division and transported for a psychiatric evaluation.

Under state law, children under 12 cannot be tried as adults. Therefore, the case against the child will be processed before the Juvenile Division of the 22nd Judicial Circuit Court of Missouri.

The investigation into the case continues and, so far, authorities have not reported whether any of the accused have legal representation.