LAPD said the incident happened Dec. 1 at around 6 p.m. in the 1600 block of Formosa Avenue.
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Video shows the two victims in an apartment building when they are suddenly approached from behind and surrounded by four suspects.
Police said the suspects were armed with handguns and took off two expensive watches from the victims.
LAPD is now asking for the public's help in identifying the suspects.
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The Follow Home Robbery Task Force at Robbery-Homicide Division is investigating the case.
A reward up to $10,000 is being offered by the FBI for information leading to an arrest.