An eight-year-old boy in South Sacramento, California, was beaten to death with a hammer, allegedly by his mother's former boyfriend, while defending his younger sister from being molested by him.

Dante Daniels was killed by Deandre Chaney Jr, 23, on Sept 1, while trying to protect his sister Danae, seven, reported The Daily Mail.

Chaney is also said to have turned the hammer and a knife on Danae and their mother Elizabeth Salone, 28. He allegedly also used lighter fluid on them.

After the attack, Dante was declared brain dead, and died six days later.

Chaney faces murder and attempted murder charges, along with a charge for lewd acts with a child under the age of 14.

According to FOX40, Dante was a third-grade pupil at Oakridge Elementary, and the day of the attack was supposed to be his second day at school.

Danae and Dante's grandmother Monique Brown said that Dante was trying to save his sister and that was why he was given the most aggressive beating.

His sister and mother survived, but Ms Salone "will probably never see out of her left eye" and Danae "will need a lot of help", reports said.

Ms Brown added that Dante's last act of kindness was to donate his heart to a four-year-old in Southern California.

There is a campaign on crowdfunding site Gofundme to raise funds for the family.

As of Monday (Sept 25) morning, it had raised US$15,571 (S$20,980) of its US$20,000 target.