Hundreds gathered for a vigil Saturday night in Westborough.
Robert Marriott told the crowd, "Together we created an angel, and tonight she is home in heaven."
Downey's daughter Nicole, who was Marriott's best friend, described Marriott as a "fun-loving and goofy" young woman who got along easily with others and had a wide circle of friends. She also was a good student who loved animals and science and volunteered at the New England Aquarium in Boston, Nicole Downey said.
"It was a shock to me when I found out she was missing. That was not like her at all," she said. "She was just all around a great person. I don't know why anyone would want to hurt her."
Mazzaglia, who graduated from the University of New Hampshire in 2006 with a bachelor's degree in theater, was active in the arts, performing in several dozen plays and musicals over the last decade in southern New Hampshire.
He also was a martial arts instructor who described himself on websites as having a black belt in karate and being familiar with several forms of martial arts and weapons. And he described other interests including juggling.
Robert Modee, a friend of Mazzaglia's and a martial arts instructor in Kittery, Maine, said he was struggling to comprehend how his friend could be charged with murder.
"I don't understand what's going on right now," he told the Foster's Daily Democrat in Dover, N.H. "I'm completely floored with all this."
Mazzaglia is scheduled to be arraigned Monday. A working telephone number for him could not immediately be located. It was unclear whether he had a lawyer yet.