Stallworth was headed toward the beach when he hit a 49-year-old man around 7 a.m., said Miami Beach police spokesman Juan Sanchez.
The unidentified pedestrian was taken to a nearby trauma center, where he was pronounced dead about an hour later. He was near a crosswalk but it's not clear if he was crossing legally.
"We are aware of the incident involving Donte Stallworth and have been in contact with his representatives," the Browns said Saturday in a statement. "We understand the seriousness of this situation, but will not have any further comment at this time as this is an ongoing investigation."
Stallworth was cooperating and no charges have been filed, Sanchez said. Officers drew his blood to test for drugs or alcohol, which is routine, but police said it was too early to tell if Stallworth was impaired or violating traffic laws. Police would not say where he was coming from or where he was headed.
A message seeking comment was left on the voicemail of his agent, Drew Rosenhaus.
Stallworth signed a seven-year, $35 million contract with the Browns as a free agent before last season but hardly played because he was hurt. He was due a $4.75 million signing bonus Friday.
He previously played for the New England Patriots.
Laporta - Cesc has Barca at heart
Primera Division round-up
Cleveland Browns sign another former Jet, ink LB David Bowens
