A librarian secretly built a $4 million fortune and left it all to his alma mater

New Hampshire resident and librarian Robert Morin led a simple life.

He lived alone, drove a 1992 Plymouth and never went out.

"He would have some Fritos and a Coke for breakfast, a quick cheese sandwich at the library, and at home would have a frozen dinner because the only thing he had to work with was a microwave," Morin's longtime financial advisor Edward Mullen told the Boston Globe.

You wouldn't know it from his lifestyle, but Morin — who graduated from the University of New Hampshire before working in the school's library for nearly 50 years — was a multimillionaire. In fact, very few people didknow, until he died in March 2015 at age 77 and bequeathed his entire $4 million fortune to his alma mater.

It was a complete "surprise to the university community," Erika Mantz, director of media relations at UNH, told CNBC. "People were honored and excited to learn of his generous bequest."

Morin's simple lifestyle allowed him to stash most of his income in a checking account and certificates of deposit, and his advisor helped him contribute to mutual funds and annuities, the Boston Globe reported: "Morin also bought several life-insurance policies over the years, all intended to benefit the university from which he earned a bachelor's degree in 1961."

He earmarked just a fraction of his generous gift, requesting $100,000 go toward the Dimond Library, where he spent the majority of his career.

"It will provide scholarships for work-study students, support staff members who continue their studies in library science, and renovate and upgrade one of the library's multimedia rooms," Mantz explained in a press release.

As for the remaining $3.9 million, Morin told his financial advisor that he trusted the school to "figure out what to do with it."

The majority — $2.5 million — will go toward launching a career center for UNH students and alumni.

Another $1 million will fund a video scoreboard for the school's new football stadium, an appropriate allocation considering the librarian became a football buff in the last 15 months of his life, Mantz said.