The man's body was found before 7am Saturday near the Franklin Street bridge. Houston police believe the victim was homeless, and they're trying to track down anyone who knew him.
Witnesses knew the man only by a nickname: Detroit. Police are describing Detroit as a black man in his 30s or 40s.
Investigators say a woman walking under the bridge discovered the bloody murder scene and called for help as she noticed the man's body floating in the bayou.
A dive team had to pull his body from the bayou. According to investigators, they can't tell if the was shot multiple times or stabbed.
Witnesses say up to 30 homeless people live under the Franklin Street bridge every night, but they were nowhere to be found when investigators arrived at the crime scene.
"There's people that stay there. They know what happened, and they disappeared. When this went down, they are gone. There wasn't nobody there but blood," Mitch Hesters said. "But you find the ones that live there. They know what happened."
Police will be canvassing the area and local homeless shelters looking for leads.
Anyone with information is urged to call police at 713-308-3600 or Crime Stoppers at 713-222-TIPS.