SAO PAOLO, Brazil (CNN) -- João Rodrigo Silva Santos didn't come home Monday night.
When the former professional footballer's wife opened the door on her way to work the next morning, she found his severed head on their front step.
The head was inside a backpack, police said. Santos' eyes and tongue had been gouged out, according to Brazilian media reports.
Now police in Rio de Janeiro are investigating the grisly killing, though they haven't said who they believe is behind it.
Santos, 35, was a forward for a number of mostly second-tier Rio de Janeiro football teams before retiring and opening a health foods store. His death comes at a time when football fans worldwide are shifting their focus toward Brazil, which will host the World Cup in 2014.
One police official told Brazil's O Globo newspaper that authorities are investigating whether a recent post on the store's Facebook page could be connected to the crime. The post showed surveillance footage and asked for help catching shoplifters.
Police plan to compare the images to surveillance footage taken at the shop Monday night, chief homicide investigator Rafael Rangel told the newspaper.
The former football player was last seen Monday night, when two suspects entered his vehicle, CNN affiliate TV Record reported.
On Wednesday morning, police said they found parts of a man's body in a river outside the city and were testing the DNA to see whether the remains belong to Santos, TV Record said.
Authorities have interviewed 10 witnesses so far in the case, police said. According to local media, Santos' wife, Geisa Silva, worked for the police in one of Rio's shantytowns, but as a social worker giving swimming lessons to children, not as a policewoman.
She told investigators she did not know of any threats made against her husband, according to TV Record.
Some of Santos' relatives and neighbors told O Globo that he didn't have any enemies and said they didn't know what could have motivated the attack.
Santos started his football career when he was 16 years old, and played for several Brazilian club teams. He played for the Bangu club team from 1996 to 2005, according to a biography on the club's unofficial website.
In 1998, he played for Honduras' Olimpia club. And in 2003 he played for Sweden's Oster club, the website says.
The website calls Santos a "humble hero," describing how goals he scored brought victory to another club team he joined. According to the FutRio.net football news site, Santos left the field earlier this year to focus on his business.
The site reported that club players in Rio de Janeiro on Wednesday honored Santos with a minute of silence.
(CNN's Shasta Darlington reported from Sao Paulo. CNN's Catherine E. Shoichet reported from Atlanta. CNN's Kevin Gallagher contributed to this report.)