A judge ruled Tuesday that a 14-year-old Montgomery County boy who killed his infant sister in February should be placed at a residential treatment center.

Jonathan Aguiluz, of Silver Spring, had been found involved -- the juvenile equivalent of guilty -- in the suffocation death of 7-month old Larissa Yanes.

On Feb. 7, the children's mother went to work and left Larissa in her brother's care. The mother returned to her Silver Spring apartment the next morning and found Larissa unresponsive, police said.

Aguiluz told police that he put his hands on his sister's nose and mouth, restricting her breathing, because Larissa was crying, according to a charging document.

When detectives saw Larissa at a hospital, they noticed several injuries on her body that were initially thought to be caused by a beating. But a medical examiner determined that these injuries were caused by post-mortem bug bites and that the cause of Larissa's death was asphyxia.

Aguiluz was initially charged with first-degree murder as an adult. But the charge was later reduced and the case moved to juvenile court. After a three-day trial April that was closed to the public, the 14-year-old was found involved of involuntary manslaughter and neglect of a minor.

During a proceeding on Tuesday, Montgomery County Circuit Court Judge David Boynton said that the Department of Juvenile Services recommended that the boy be removed from his home and community, be in a secure facility and receive treatment that included behavior modification. Boynton then said that the court has determined that Aguiluz go to a residential treatment facility.

After the hearing, Mary Siegfried, the teen's lawyer, described the treatment center as a juvenile facility with a large therapeutic component. In juvenile court, no specific sentence lengths are set, but Aguiluz can remain under the court's jurisdiction until he is 21, Siegfried said.

Lydia Guillen, a family friend of the teen, said that Aguiluz was a good kid and that she thinks he will be OK after undergoing therapy.

"No, he won't hurt nobody," she said.

The 14-year-old has been accepted by a treatment center, but before he can be moved, a "certificate of need" has to be obtained and there needs to be bed space. A hearing was scheduled for later this month to address the status of Aguiluz's placement, Boynton said.