Bell, 47, was killed early Sunday as he was walking to his car after closing his business, the Literary Cafe and Poetry Lounge.
The Miami Herald reported a car occupied by at least two men pulled alongside Bell, and one man jumped out and shot him several times with a large-caliber weapon. Bell died at the scene.
Police said the shooter didn't take any of his possessions, which included cash and jewelry.
"We don't have a motive right now," said Lt. Neal Cuevas of the North Miami Police Department.
Witnesses in the cafe the night of the shooting gave police conflicting descriptions of the suspects' car.
Addonis Parker, a Miami poet and artist, said Bell's audiences loved him.
"What made him different is the element that he came out of, and what he made of his misfortunes. He turned his unfortunate events into gold," Parker said. "The stuff he said, everybody was electrified every time he opened his mouth because you could relate to it."
Bell served time in jail for selling cocaine when he was a young man and he got his start ghost-writing love letters for other inmates.
Lytro unveils camera that can focus a photo after shooting it
'How to Train Your Dragon 2' releases 5-minute clip