Walker, 23, was riding an off-road dirt bike without a helmet or headlights at around 8 p.m. when he collided with a Ford Escape SUV at an intersection, Detective Dan Ferrin told WBAL. Walker was wearing dark clothing, including a Ravens jersey, Ferrin said.
He was taken to a trauma center following the crash, according to Miami-Dade police. The woman driving the SUV was not hurt.
Ferrin noted that motorcycles, including dirt bikes, are required to have headlights and a license plate.
"Tray was a young man with a good and kind heart. He was humble and loved everything about being part of the Ravens' team," coach John Harbaugh said in a statement.
On Twitter, players and fans expressed their grief and offered condolences.