The 24-year-old British actress best known for her role as Hermione Granger in the "Harry Potter" movies was one of more than 2,000 students to get her degree from the Ivy League university in Providence on Sunday.
She was photographed sitting and walking next to a woman who was wearing a cap and gown. The same woman, who was older than Watson and her fellow graduates, was later seen escorting Watson without a cap and gown and with a holstered weapon, a badge and other equipment.
When asked if the woman was a campus police officer and why the guard was necessary, Brown spokesman Mark Nickel said today he was "not able to help."
Watson began her studies at Brown in 2009, the same year she was named the highest-grossing actress of the decade by the Guinness Book of World Records. She earned a degree in English literature.
Her most recent movie is the Biblical epic "Noah," and she has also starred in "The Perks of Being a Wallflower" and "This is the End."