Authorities were looking for a man with a history of violence and a prior drunken driving arrest who came barreling down a residential street at twice the speed limit in a car he didn't own and crashed into a pregnant woman and her husband, killing them and ultimately the child they were expecting.

Police identified the suspected driver as Julio Acevedo, and said he was speeding down the Brooklyn street in a BMW at 95 km/h early Sunday when he collided with another car carrying Nachman and Raizy Glauber, both 21. They died Sunday, and their premature son died Monday.

Acevedo, 44, was arrested last month on a charge of driving while under the influence, and the case is pending. He served about a decade in prison in the 1990s for manslaughter. No one answered the door at Acevedo's last known address, in a public housing complex in Brooklyn. Neighbours said his mother lived in the same building, but she did not answer her door.

A close-knit ultra-Orthodox Jewish community in Brooklyn was in mourning, and their grief worsened following the baby's death. The child had been delivered by cesarean section after his parents were killed.

The baby weighed only about 4 pounds when he was delivered, neighbours and friends said. He died of extreme prematurity, the city medical examiner's office said.

The baby was buried near the fresh graves of his parents, according to Isaac Abraham, a spokesman for the Hasidic Jewish community. About a thousand community members turned out for the young couple's funeral a day earlier.

'We all hoped the baby would survive'

"The mood in the neighbourhood is very heavy," said Oscar Sabel, a retired printer who lives near the scene of the accident. "We all hoped the baby would survive."

Brooklyn is home to the largest community of ultra-Orthodox Jews outside Israel, more than 250,000. The couple wed last year in a marriage arranged through a matchmaker and were living in the Williamsburg neighborhood.

They were members of the Satmar Hasidic sect, whose men dress in dark coats and hats, wear long beards like their Eastern European ancestors and have limited dealings with the outside world. Raizy Glauber grew up in a prominent rabbinical family. Her husband was studying at a rabbinical college; his family founded a line of clothing for Orthodox Jews.

Sabel, dressed in the traditional long black coat of the Satmar, said it was a terrible tragedy.

"But it's what God wants," he said. "Maybe the baby's death, and his parents', is not for nothing; God doesn't have to give us answers."

Shortly after midnight Sunday, Raizy Glauber, who was seven months pregnant, wasn't feeling well, so the couple decided to go to the hospital, said Sara Glauber, Nachman Glauber's cousin. They called a livery cab, a hired car that is arranged via telephone, not hailed off the street like a yellow cab.

The livery cab had a stop sign, but it's not clear if the driver stopped. Police said the crash with the BMW reduced the cab to a crumpled heap, and Raizy Glauber was thrown from the wreck. The engine ended up in the back seat, Abraham said.

Police said the driver of the BMW ran away.

The driver of the livery cab, Pedro Nunez Delacruz, was knocked unconscious but was not seriously hurt. His vehicle should not have been sent to pick up the passengers because an application to use the Toyota as a livery cab had not yet been approved, the city Taxi and Limousine Commission said.

"We in the community are demanding that the prosecutor charge the driver of BMW that caused the death of this couple and infant ... with triple homicide," Abraham said in a statement. "This coward left the scene of the accident not even bothering to check on the people of the other car."

How Acevedo came to possess the BMW is also under investigation. The registered owner, Takia Walker, was arrested on insurance fraud charges Sunday in a scam involving the car, police said. She was not involved in the crash. A telephone number registered to Walker rang unanswered.

A person familiar with the investigation said Walker bought the car legally, or allowed her identification to be used in the purchase, then gave the vehicle to a middleman who either lent or rented it out to the driver. The person was not authorized to speak publicly and spoke to The Associated Press on condition of anonymity.