"He could have been killed anytime between Tuesday night and Saturday afternoon. That would be the times the public should concentrate on," Detective Mark Morgan, Los Angeles Police Department.
Investigators say finding a motive for the killing will be key.
"We are meeting with his employers, the victim's employers, friends, family. Interviews are going on as we speak," said Detective Morgan.
Detective Morgan asked family members about a separate murder case on Tuesday. The case involved Ricardo's sister, Rosalba Contreras, who was also a realtor.
Rosalba was convicted of stabbing an elderly couple in a San Pedro home in September 1998, and then setting it on fire. According to court documents, Rosalba Contreras befriended 78-year-old Valentine Partida, and then stole $650,000 from him and his 91-year-old wife, Elvira.
A report in the Daily Breeze named Ricardo Contreras in a wrongful death civil suit for notarizing fraudulent documents in the scheme.
"Whether that has anything to do with it, we have no idea right now," said Detective Morgan.
Ricardo Contreras's family has been working on funeral arrangements. However, on Tuesday afternoon, they were trying to determine whether the case involving Rosalba Contreras may have spurred a revenge murder.
The Contreras family told Eyewitness News they are defensive about the conviction of Rosalba Contreras. They say they want to pursue an appeal, but they don't have any money to do it.
If you have any information about Ricardo's murder, you are asked to call (877) LAPD-24-7, or (877) 527-3247.