It is reported that Eduardo Villarreal, 21,smashed his pick-up into the house after rowing with baby Naomi's mother, Trudy Bonilla, over access.
Detectives investigating the incident in Los Angeles have told KTLA-TV they don't believe it was an accident.
Villarreal is said to have snatched the baby and run down the street with her before a relative convinced him to return her to her mother. He then came back in his truck.
Officer Mike Lopez told reporters the young mother was found dead in the house, whilst the newborn baby died shortly afterwards in hospital.
'When we got here the truck was practically halfway inside the home,' he said.
Deputy Chief Kirk Albanese said Villarreal had deliberately and intentionally drove the vehicle into the house.
Villarreal told investigators he had meant to commit suicide but not hurt anyone else.
It is thought around 14 other people were in the building at the time of the crash, which was said to have happened at 11.42pm.
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