Alo Ngata, 29, died in police custody on Wednesday morning after an altercation in the central suburb of Freemans Bay on Sunday.
Police tasered and restrained him after witnessing him attacking an elderly man, Superintendent Karyn Malthus said.
The friend, who did not wish to be named, met Ngata when the pair were studying at Tangaroa College in Ōtara.
He described the 29-year-old as "fiercely loyal" and coming from a large family.
"I saw him just a couple of months ago in town and he was still just the same humble as guy I knew in school."