A 3-week-old baby has been shot and killed in front his two young siblings.

A three-week-old baby boy has died after he was ‘caught in the crossfire’ in a targeted car shooting in Las Vegas.

According to NEWS3 Las Vegas, baby Marcus Thomas Jr’s father was pulling him out of his car seat when someone started shooting at the parked vehicle.

Two other children and a 19-year-old woman, who was driving, were also caught in the attack.

Marcus' siblings were not harmed, but his father was shot four times and survived.

The Clark County Coroner's Office confirmed the three-week-old died from multiple gunshot wounds.

The baby's cousin, Ava Loftis, told NEWS3 Las Vegas the person, or persons, responsible for the shooting were "cowards".

"It's tearing me up. I can't even sleep because I keep seeing this innocent, itty bitty baby that couldn't do nothing to nobody and he's dead for no reason," she said.

"I don't know who would do this. Turn themselves in. You just killed an innocent newborn baby. He didn't even get to see two months of his life."

Police are still searching for whoever is responsible for the shooting, but they believe it was a targeted attack on Marcus's family.

The baby's aunt has set up a GoFundMe page to help fund the newborn's funeral.

"They had no idea that on that day, they would be facing a tragedy so traumatising that would change their lives forever," she wrote.

"This is a very hard time for my family...please keep us in your prayers...A beautiful life taken so soon!

"Never would we have thought we would be planning a funeral for our three week old baby boy instead of celebrating his turning of one month old."