A Catholic school that lost one its old boys in the Christchurch mosque attacks has paid tribute by performing a spine-tingling haka and waiata for their fallen brother.

Over the weekend St Thomas of Canterbury College, a Catholic school, learnt they had lost ex-student and Muslim friend Hussein Hazim Al-Umari during the attack that killed 50 people.

In honour of Al-Umari and the other 49 victims, Head Boy Cameron Brewitt and a large number of pupils and ex-students organised to pay their respects by visiting the outside the mosque at the Students' Uniting in Love Memorial.

Wanting to represent their school St Thomas, the boys sung a Fijian hymn and performed their moving school haka.

"After this tragedy, we felt so compelled to show our support and solidarity to these victims a way that represented our school and our community," Head Boy Cameron Brewitt told the Herald.

"After vigils, the rest of the schoolboys and I wandered down opposite the mosque near Hagley Park to perform a Fijian hymn and haka in a way to acknowledge our thoughts in a St Thomas' way.

"We had a really large contingent of boys in attendance to the prayer, speeches and song, with St Thomas students leading the way at the memorial.

Hussein Hazim Al-Umari died protecting others, said his mother.

"It speaks volumes of the connection, passion and pride that the boys hold in the school and in the city. It has become a trend and part of the culture of the school in a way.

"We felt compelled to contribute our own song and haka to let our emotion out and show that we as St Thomas stand in solidarity with the victims of this tragedy.

"What followed was one of the most powerful and emotional songs and haka that I and many of the boys have ever taken part in at school."

St Thomas Of Canterbury College might be a Catholic school, but they welcomed Al-Umari, a Muslim, into their community.

Al-Umari attended St Thomas between 1998 and 2001.

He was born in Abu Dhabi but moved to Christchurch with his family in 1997.

Brewitt says he is proud his Catholic school is inclusive of other religions and cultures and said Al-Umari's death has rocked the St Thomas community.

"Hussein attended from 1998 until 2001. We have a few teachers currently here that taught him and some who attended school with him. It really hit home that one of our own was taken in this tragedy.

"The school respects different cultures and religions. The diversity in our school really highlights the respect and the amount of outpouring for this tragedy again highlights the respect we have for everyone no matter what ethnicity you are or the religion you follow."

Al-Umari's mother, an Iraqi calligraphy artist named Janna Ezat, announced on Facebook that her son was killed at the Al Noor Mosque.

"It is with great sorrow we came to know our son Hussein Hazim Hussein Pasha Al-Umari is a martyr," she said.

"Our son was full of life and always put the needs of others in front of his."

In a tweet, Ezat said her son was one of the first people to protect other people praying at the mosque.

"The friends of martyr Hussain Al Umari are talking about the way my son defended other worshippers at the mosque. He was one of the first to take a bullet and save the lives of those around him, and helped them to escape."