But that all changed late last month after Mr Mangal was forced to go public thanks to a New York State law which prevents lottery winners from remaining anonymous.
Speaking to reporters this week, he said he still had no plans to quit his job.
"I like working," the New York Post reported him as saying, adding that his colleagues were only "finding out now" about his win.
Mangal, who lives with his wife in a "humble" ranch home but who has no children, also had a stern warning for any long-lost relatives hoping to cash in on his good fortune.
"If I didn't know them two weeks ago, I don't know them today," he joked.
He told reporters he didn't realise he was a millionaire straight away.
"The ticket sat on my kitchen table for a week because I was out of town," he said.
"I really don't check the ticket that often. Who's going to think they won the lotto?"
Apart from taking a trip to Hawaii, Mr Mangal does not have any big plans for his cash yet — however, he has already sought the advice of a financial planner.
"I'm going to invest some, pay off my bills, my debts. I'm pretty sure at some time, I'll buy a new car … I always wanted to travel, so I'm pretty sure I'm going to travel. I would like to go to Hawaii," he told the New York Daily News.
He told the publication he was now retiring from playing the lottery, because: "It's time for someone else to win."
The supermarket that sold Mangal the wining ticket will also score $US10,000, which will be donated to charity.
