Dae'von Bailey was found dead inside a South L.A. home on the 800 block of East 87th Place last Thursday. Police said the boy had multiple, unexplained injuries on his body that showed continual abuse.
Police say Fisher, 36, was the last known caretaker of the child, but he was gone from the home when paramedics and officers arrived.
Police searched the area around 90th Street and Avalon Boulevard for hours Tuesday night after someone spotted Fisher. But despite a foot chase and an aerial search, Fisher was able to get away.
Officers had been handing out fliers with Fisher's pictures, asking for help from residents.
Dae'von had been living with Fisher since December under an agreement with the boy's mother, and it was approved by Child Protective Services. The boy's mother told Eyewitness News last week that she had left her son with Fisher while she sorted out personal matters.
Dae'von was the subject of about a dozen calls to the county's child abuse hotline prior to his murder, but the case was never brought to the attention of the LAPD.
The district attorney's office is also considering filing charges against those individuals who may be harboring Fisher or interfering with the criminal investigation.
"We believe that Marcas Fisher is still in this area," said LAPD Cmdr. Pat Gannon. "We believe that there are individuals that have decided to harbor him for whatever reasons they may have. If that is their, what they choose to do in this particular case, we will pursue them in addition to Marcus Fisher."
Fisher has been convicted of rape and has a previous domestic violence arrest.
Police are asking for the public's help in the case. Anyone with information is asked to call the LAPD at (877) LAPD-24-7, that's (877) 527-3247.