A part-time Hawaii resident who once worked as a janitor, cared for two nonagenarian sisters and owned a painting claimed to be a $40 million treasure by a famed abstract expressionist died earlier this year after a long and unfinished struggle to authenticate his most prized collectible.

Douglas Bruce Himmelfarb was 64 when he died in Los Angeles from cardiac arrest in February.

However, his quest to validate the painting, which drew international media attention, lives on.

The painting is now part of Himmelfarb’s probate estate, and Honolulu attorney Chris Muzzi has been approved by a state judge to settle the estate in an effort that will predominantly focus on the still-daunting and conspiracy-charged task of determining whether the picture of three colored rectangles is indeed the work of American master Mark Rothko.

“We’re going to do whatever we need to do to maximize the value of this,” Muzzi said. “It’s not going to be dumped.”

Himmelfarb, who grew up in a suburb of Washington, developed an interest in art at a young age and said he bought his first painting when he was 8. To support his collection habit later, he said he did all sorts of work from construction to being a janitor.

“I worked my butt off so I could buy antiques and art,” he said in a 2014 interview.

It was at a small auction in 1987 where Himmelfarb said he saw a painting titled “Ex. No. 7,” bought it for $319.50 and then set out to show beyond industry doubt that it was painted by Rothko, who took his own life in 1970.

Himmelfarb was a colorful character who told offensive jokes, described himself as a botanist by hobby and became the guardian of two unmarried sisters three decades his senior.

The sisters, Ruth and Ella Hirshfield of Bel Air, Calif., named Himmelfarb their legal heir and gave him commercial real estate they had inherited, including an old courthouse in Malibu that Himmelfarb converted to restaurant use.

In 2006, Himmelfarb leveraged the real estate to buy the historic Marks Estate mansion in Nuuanu for $4.4 million as a part-time residence for himself and the sisters who he said had become “more my family than my own family.”

Three years ago, with the Hirshfields in their mid-90s, Himmelfarb was facing foreclosure on the mansion in the midst of renovation after being unable to keep California real estate investments from souring in the wake of the recession. Yet he figured all would be fine because he had a $40 million asset.

The value was his own estimate, but perhaps wasn’t crazy given that Rothkos had sold for $72.8 million in 2007, $33.7 million in 2011 and a record $87 million in 2012.

Himmelfarb, who owned Ex. No. 7 with art collector Anders Karlsson holding a 25 percent interest, had been working for more than two decades to document his painting, and expected the work to be included in a “catalogue raisonne” documenting all known Rothko paintings on canvas assembled by David Anfam, the world’s foremost expert on the artist.

Generally, paintings included in such catalogs are accepted as authentic by art investors and major auction houses.

But when the catalog with 834 paintings was published in 1998, Ex. No. 7 wasn’t in it.

Himmelfarb believed Anfam excluded it as payback for an insult. Himmelfarb had been excited after he heard about a photographic negative of what looked like Ex. No. 7 in Rothko’s personal files. Himmelfarb said that after Anfam expressed uncertainty over the negative’s origin, Himmelfarb sarcastically asked whether Anfam thought Himmelfarb put it in Rothko’s files. And then Himmelfarb said he called Anfam a “(expletive) imbecile.”

Anfam didn’t respond to requests for comment.

With Himmelfarb in financial distress, he filed for bankruptcy in 2013 and with Muzzi’s help used U.S. Bankruptcy Court subpoena power to obtain a copy of the black-and-white negative.

A manager of Rothko’s estate submitted the copy after much legal wrangling, but attached a disclaimer that said no one should conclude that the negative originated from the artist or his family, and advised against “drawing any undue inference of authenticity” for the painting.

Himmelfarb was astounded, and described his ordeal as a dark comedy. “The only thing that gets me through this is my sense of humor,” he said in 2014 as his other art and collectibles were prepared for auction to pay creditors on the eve of foreclosure.

When Himmelfarb died, he still owed creditors about $2.3 million. Muzzi said repaying those debts hinges on selling the painting at a Rothko value.

One pall over the prospect of selling the painting, Muzzi said, was a federal court trial last year involving a New York art dealer who sold a forged Rothko to a collector for $8.3 million in 2004.

“That kind of put a chill on things,” he said.

Colette Loll, founder and director of Washington, D.C., consulting firm Art Fraud Insights, said quite a few possible masterworks are in a “painting purgatory” that emerged in recent years because art foundations and experts that used to help authenticate works now fear being sued.

“It’s just a legal minefield, and people just aren’t willing to do this anymore,” she said.

At one time, the National Gallery of Art in Washington, which published the Anfam catalog with Yale University Press, considered publishing an addendum but has no plans for that now, according to spokeswoman Anabeth Guthrie.

Still, it’s not impossible to establish a painting as a real Rothko just because it wasn’t in Anfam’s catalog. Auction house Christie’s notes that 10 Rothko paintings have surfaced since the 1998 catalog was published, and one was the $33.7 million masterpiece dubbed “Untitled #17” that sold in 2011.

One key factor in helping determine the authenticity of a painting can be its documented history. According to a 2014 story in The Australian, Himmelfarb claimed to have traced his painting to Los Angeles collector Mollye Teitelbaum, who sold one of two similar paintings to the auction house where Himmelfarb made his purchase. The other painting, “Ex. No. 4,” is owned by Teitelbaum’s son, Murray, the article said.

Peter Selz, a former curator of the Museum of Modern Art in New York who curated an exhibit of Rothko’s work and has seen Ex. No. 7, said the history, or provenance, of the painting is pretty clear in his mind. “There’s nothing funny about the provenance,” he said. “There’s no question in my mind that this is the real thing.”

Muzzi said his goal is to gather sufficient evidence so that the painting can be sold at a well-publicized and well-regarded art auction. “Unfortunately it’s a very slow process,” he said.

Besides creditors, the only beneficiary of Himmelfarb’s estate is Anatoly Rosinsky of California.

Himmelfarb, who added a second “m” to his family name to reflect how he understood it was originally spelled, is survived by mother Frances Himelfarb; and brothers Steven, Gary and Stuart Himelfarb. Ella Hirshfield died recently. Her sister, Ruth, turns 100 this year.