The investigators, who had come to the factory on Dikeman Street to look into allegations of illegal dumping, had caught a whiff of the hidden drugs and a glimpse of an odd-looking wall while probing around the garage. They told Mr. Mondella they would come back with another search warrant. He said he had to use the bathroom.

In the days after Feb. 24, the investigators would find hundreds of thousands of dollars in cash and several more luxury cars. They’d find sophisticated grow lamps and irrigation equipment. They’d find an underground office with a small library of dusty horticultural books. They’d find a copy of The World Encyclopedia of Organized Crime.

But they still haven’t found the answers to fundamental questions about Mr. Mondella’s secret life: How did he operate what one law enforcement official involved said was the largest indoor marijuana growing operation any of the investigators had ever seen in New York City, and what drove him into the drug trade? Why did he unravel so quickly, killing himself before so much as consulting one of his many lawyers? His family appears to have been ignorant of his other life, and his iPhone’s contents are locked.

At 57, Mr. Mondella seemed to have stepped out of an old Brooklyn movie, a tall, gravel-voiced, hard-bargaining man who charmed women, impressed men and was said to shoulder all the burdens of his family and of many of his employees, too. He would do almost anything for the people he cared about, his friends said. He killed himself, some of those closest to him say, because he couldn’t face his family, or because he wanted to spare them.

“Everyone who truly knew our father knows he was a loving, caring, generous man with a tough exterior,” his daughters, Dominique Mondella and Dana Mondella Bentz, said in a statement. “We have many special memories of our father and love and miss him very much.” The sisters, along with their father’s sister, Joanne Capece, have assumed leadership of the company. They declined to be interviewed for this article, though they answered some specific questions about the company through a spokeswoman.