"He was 93 and he had a great life," he told the Herald.
"He'd been unwell for some time, since late last year. But you can never prepare yourself for such an eventuality."
One of his strongest memories was Mrkusich's comments after he received one of the inaugural Icon Awards in 2003.
The awards were created by the Arts Foundation of NZ to redress what was seen as historic indifference to the arts in this country.
"When he received it ... he said that he had inspired young artists to keep going when times were tough and just to do what you want to do," Lewis said.
Mrkusich was of Dalmatian descent. While Dalmatians are known in New Zealand for success in industries like winemaking and farming, not many are known for their art.
"It's just a freak of fate," Lewis said. "His parents weren't into art, he got into it himself and was always interested right from when he was a teenager."
Mrkusich was recognised with his first retrospective exhibition at the Auckland City Art Gallery in 1972.
His work is probably best known by Wellingtonians and overseas visitors, being most publically displayed in the capital through the large plates of coloured enamel windows on the Te Papa building - a commission Milan won in 1994 amid fierce competition.
Aratoi Museum of Art and History in the Wairarapa, which exhibited some of his works, described him as New Zealand's pre-eminent modernist artist and said it was saddened by his death.
"It is always a sad day when a great artist dies," the organisation said on its Facebook page.
"Aratoi salutes Milan Mrkusich's lifetime of work, his generosity, and the ways in which he enriched the visual arts of our country."
A small funeral is planned for family members only.
