NEW YORK (CBSNewYork) — The investigation into the deaths of two toddler siblings in the Bronx continues after the medical examiner ruled they died of blunt force trauma to the torso.

The medical examiner ruled the deaths of both children, 3-year-old Micah Gee and his 2-year-old sister Olivia, as homicides.

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“They’re defenseless,” said neighbor Edith Brownbroyant. “There’s nothing they could do to hurt you. Why would you want to hurt them?”

That question and who could be responsible is what investigators are now working to determine, CBS2’s Janelle Burrell reported.

Olivia and Micah Gee (Credit: Facebook/Greg Gee)

The brother and sister lived at the Amalgamated Housing co-op on Van Cortlandt Park South in the Bronx. Sources tell CBS2 that their mother, 31-year-old Jade Spencer, told police that the toddlers went to bed before her boyfriend got to their apartment around 9:30 p.m. Sunday.

Sources said she told them they smoked marijuana, drank beer and watched a movie before falling asleep. Then around 1:15 a.m. Monday, she said the boyfriend, 31-year-old Novell Jordan, told her something was wrong with the children.

Both tots had severe asthma and she said Micah was having trouble breathing. Olivia was unresponsive and both had injuries to their necks.

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The toddlers were taken to Montefiore Medical Center, where they were later pronounced dead – Olivia just three minutes before her brother.

The children’s grandmother is the educational director at the co-op, where the family is well-known and well-liked. The community is now struggling to understand how this could happen.

“Very sad,” said neighbor Yefim Zonopolskiy. “It’s terrible.”

“The worst thing we could actually imagine,” said Charles Zsebedics, the co-op general manager. “This is not something we could ever think of.”

Both the mother and her boyfriend were questioned by police Monday. Spencer was taken to a hospital for a psychiatric evaluation, where she remained Tuesday evening.

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Jordan has obtained an attorney and police are now consulting with the Bronx District Attorney as to how to proceed in the investigation.