Ella Ensor and her pet lamb Crystal (Facebook)

Ella saw her lamb Crystal tied to a fence and being kicked multiple times on the left side of her stomach.

The family says the boy was around 13 or 14 years old, with blonde hair and wearing a black hoodie.

Another boy was with the aggressor, who told him to stop kicking the animal. Ella also asked him to stop.

The family took Crystal home, where she died within the hour from severe internal injuries.

Now the family and the SPCA want to track the abuser down to share with him the grief the family has gone through because of his actions.

Sarah Ensor, Ella's mother, wrote an emotional post on Facebook, which has already been shared more than 2000 times.

"Nothing will ever bring our gorgeous Crystal back but I want knowledge to be taught to children in schools about how to treat and care for animals," it reads.

Ms Ensor says she does not hold the school responsible in any way: "Oropi School Calf Club was absolutely amazing but it was all ruined for myself and my family by the actions of this boy."

Oropi School Principal Andrew King says the day was a memorable one but is saddened to be appealing for any reports of what happened after the school's event.

"This is a very devastating situation for the family to have gone through and on behalf of the school I wish to pass on our condolences, particularly as the lamb had won the competition and Ella was going to represent Oropi School at Group Day," Mr King said in a statement.

"The school would like to know if anyone noticed any unusual behaviour from a person during the day."

Mr King says so far students, teachers and support staff have been unable to help with any additional information.

Mr Ensor is calling the attack "animal abuse of the highest degree" and is urging anyone with information to contact her personally or call the SPCA on (07) 578 0245. Oropi School can also be contacted on 07 543 1479.

Newshub.