The witnesses said the man walked into the Brookline Avenue location Thursday, said "I'm rich, I'm rich, I'm rich!" and threw the approximately 100 $1 bills into the air, WFXT-TV, Boston, reported Tuesday.
Nutritionist Tara Mardigan said she and the other customers stood in stunned silence after the man calmly walked out of the store.
"We all just sat there stunned. Nobody scrambled for the money like you would think they would," Mardigan said.
She said store workers told her the money was collected and donated to relief efforts in Japan.