The 21-year-old mother and her young daughter were living in the apartment and Rivera stayed with them, a police spokesman said.
NY police officers encountered a grisly scene inside an eighth-floor Brooklyn apartment Saturday, April 20, where they found a partially decapitated woman with severed fingers laying unresponsive in the living room.
When medics arrived, she told them there was a dead body in her eighth-floor apartment and her child was also inside, sources told the Post.
The New York Post reports that the woman, 21, called an Uber to a building within New York City Housing Authority's Bushwick Houses, and got into the waiting auto shortly before 1:30am, police sources said.
The driver, noticing that she was covered in blood, then called police.
Authorities are looking into whether an axe found in the block's rubbish compactor was the murder weapon.
NYPD Brooklyn North Deputy Chief Michael Kemper described the incident as a "brutal vicious attack" and said the incident was not random.
Police have arrested 34-year-old Jerry Brown in connection with the killing, an NYPD news release said.
Hours later, crime scene investigators could be seen inside the closed-off building dusting for fingerprints and examining the lobby.
Angela Valle, a 21-year-old who also lives there, was critically injured. A 4-year-old daughter of the wounded woman was in another room, but was unharmed.
Police responded to a call at the Bushwick Houses located at 811 Flushing Avenue shortly after 1.30 am.
The two women were either friends or relatives, police said.
EMS removed the child to the hospital for evaluation and observation. Residents came and went under a light rain as yellow police tape secured the building's entrance.