A 14-year-old White Oak boy has been charged with first-degree murder after admitting he smothered his infant sister.

Montgomery County Police said that Johnathan Aguiluc killed his 7-month-old sister Larissa Yanes while she was under his care. Police received a call at about 6:26 a.m. on Friday morning reporting a pediatric injury. When police arrived at an apartment on the 11600 block of Lockwood Drive, they found Larissa unresponsive.

The baby was transported to Holy Cross Hospital, and was pronounced dead at approximately 6:54 a.m. Larissa Yanes lived at the address, though it is unclear whether Aguiluc did as well.

According to detectives, Aguiluc was watching Larissa while their mother, 39-year-old Gloria Yanes was at work. She left at 10:30 p.m. on Thursday evening and planned to return the next morning.

At some point in the night, police say Aguiluc beat his sister and she began to cry. He then covered her mouth and nose area with his hand to get her to stop crying. He then placed her in a car seat that was inside the apartment, though police said they do not know why.

Aguiluc admitted to harming his sister when he was interviewed by police.

When Gloria Yanes returned home at about 6:30 a.m., she assumed the child was asleep. Larissa did not respond when her mother tried to wake her, prompting Gloria Yanes to call police.

Police said they do not know a motive in the case.

Aguiluc has been charged as an adult. He is currently in jail and being held without bond, though a bond review hearing is scheduled for Monday in Rockville at the Montgomery County District Court.

Montgomery County police Spokesman Capt. Paul Starks said he could not confirm what kind of injuries Larissa sustained, he also said detectives were releasing limited information on the case, as the investigation is ongoing.