He came to New Zealand in October 2011 on a student visa and was granted refugee status two years later.
Immigration officials had sought to revoke his refugee status in 2018, but he appealed and at the time of the attack a final decision had yet to be made on whether he could be deported.
His uncertain immigration status was also the reason why the terrorist could not be identified until 11pm Saturday night, when it was lifted by a High Court judge, as anyone claiming refugee status cannot be identified by law.
They confirmed this morning no decision had been made on what would happen with the terrorist's body.
Muslims bury their dead quickly - within 24 hours.
The dead must be interred without a casket, facing the holy city of Mecca.
Cremation and embalming are forbidden.
Assistant Commissioner Lauano Sue Schwalger told the Herald that a forensic examination of the body has been completed.
"Police have been liaising with family members overseas and we are working with them to facilitate how the body will be buried," she said.
"This is still being discussed and there is no further update at this time."
Samsudeen's brother Aroos issued a statement late on Saturday after his name was released.
The name was initially suppressed but the courts allowed it to be published - along with his criminal history and a timeline of his offending in New Zealand and immigration battle - at 11pm.
"We wish to begin by saying that our family would like to send our love and support to those who were hurt in the horrible act yesterday," said his brother on behalf of the wider family.
"We are so shaken by what has happened and we do not know what to do.
"We hope to find out with you all, what happened in Aathil's case and what we all could have done to prevent this.
"We are heartbroken by this terrible event."
Aroos claimed his brother was "suffering from some mental health problems" and had declined over the past 10 years.
"He suffered a lot during his political torture at home," he said in the statement.
"We were grateful he found the country where he wanted to live.
"We saw his mental health got worse and worse ... He spent a lot of his time in prison and was always struggling with some court cases.
"When we heard that he was in prison in New Zealand, we thought it would do him some good but didn't realise he would spend so much time there. He also had many problems in prison. He always wanted help and support. He told us that all the time."
Aroos revealed members of the terrorist's family visited New Zealand in 2013.
"We love your country and your people and we know from what we have seen since the Christchurch attack that you are good people," he said.
"I pray that God will help us all to heal from this very sad day," he said.
"We are thinking of you all. We are thinking of our parents. We are thinking of the boy who left us and the innocent people were injured yesterday.
"Our lives have changed forever.
"We realise that it will take us some time to come to terms with this. We are thinking of the injured, both mentally and physically. May we all heal from this together."
WHERE TO GET HELP:
If you are worried about your or someone else's mental health, the best place to get help is your GP or local mental health provider. However, if you or someone else is in danger or endangering others, call police immediately on 111.
OR IF YOU NEED TO TALK TO SOMEONE ELSE:
• LIFELINE: 0800 543 354 or 09 5222 999 within Auckland (available 24/7) • SUICIDE CRISIS HELPLINE: 0508 828 865 (0508 TAUTOKO) (available 24/7) • YOUTHLINE: 0800 376 633 ,free text 234 or email talk@youthline.co.nz or online chat. • NEED TO TALK? Free call or text 1737 (available 24/7) • KIDSLINE: 0800 543 754 (available 24/7) • WHATSUP: 0800 942 8787 (1pm to 11pm) • DEPRESSION HELPLINE: 0800 111 757 • SAMARITANS – 0800 726 666.