The baby was found in an alleyway adjacent to a building downtown Los Angeles at about 5:30 a.m., according to authorities. At one point, passersby performed CPR on the newborn before officers and personnel from the Los Angeles Fire Department responded.
LAFD pronounced the newborn dead at the scene.
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Investigators said the baby was possibly dropped from a fourth-floor bathroom window after the mother gave birth. Around the same time as the incident, a woman was taken to the hospital because she was bleeding from her pubic area, LAPD said.
According to LAPD, officers responded to the hospital and located the woman, who was detained and then released pending further investigation.
No further details were immediately known.