On a back wall of the underground impound lot in Los Santos, there appears to be a police officer repeatedly punching and beating a pedestrian. The pedestrian will have his/her hands raised, as if he/she is surrendering. Another police officer can be seen standing nearby, holding a pistol in case anything gets out of hand.
It is possible that this is an Easter Egg made by Rockstar, to humorously illustrate the alleged police brutality that occurred in California during the 1990s.
What is strange is that, even if you kill both policemen, the pedestrian will not move from his spot, and he will just stand there with his hands up until you kill him/her. However, injuring the pedestrian with a weapon will make them put their hands down and either fight back, or run in place. It is still unknown why the ped does not make any attempt to run away or defend itself, but it could be simply because the ped was not programmed to do so.
This myth may be in Easter Egg, as it could be referencing the large amounts of police brutality in 1992, most notably the Rodney King case, in which four police officers were acquitted after they were videotaped beating Rodney King in Los Angeles in 1992. The acquittal of the officers was a primary factor for the 1992 Los Angeles riots.