US man suspected of killing his four kids
Crime scene tape (

A US man who allegedly shot and killed his four young children and their grandmother was being questioned by police on Monday.

The four children, who were all under the age of 12, were declared dead at the scene in the small town of Lancaster, near Los Angeles.

The children's grandmother, who was in her 50s, also died in the shooting on Sunday evening.

All five victims had gunshot wounds to their upper bodies, law enforcement officers said.

The Los Angeles County Sheriff's office said Germarcus David, 29, had been arrested on suspicion of the multiple murders, and was being held on $2 million bail.

The Los Angeles Times reported that David is a security guard whose firearm licence had been cancelled.

The paper quoted a man named Waki Jones, who said he had been taking the two eldest of the children -- Amaya, 12, and Demarcus, aged nine -- to elementary school and daycare for several years.

"Amaya was a sweet girl...She was always protecting her brother, making sure he was safe at school," Jones told the paper.

"It’s just unbelievable. I can’t believe they’re gone."

Gun violence is a huge problem in the United States, fueled by lax gun laws and an abundance of firearms, campaigners say.

Liberal attempts to restrict ownership are frustrated by a powerful minority in the pro-gun lobby, who point to the 2nd amendment to the US constitution which provides for the right to bear arms.