An elusive assailant known as the Civic Center Slapper -- or possibly a copycat -- has struck again in Los Angeles, punching a federal prosecutor in the jaw, police said on Thursday.

The bold attacker struck his latest victim as he walked near a federal courthouse in downtown Los Angeles on Friday evening, knocking his head into the side of the building, a police spokesman said.

The 51-year-old assistant U.S. attorney was not identified by authorities and it was unclear if he was injured.

Police believe the suspect is responsible for two other such attacks in downtown Los Angeles over the past few weeks attributed to the so-called Civic Center Slapper.

One of those incidents came after police arrested another man, identified as Jermaine Moran, on January 20 on suspicion of carrying out a string of four similar assaults.

We know the suspect is not Jermaine Moran because he is still in custody on four other charges related to slapping people, Lieutenant Paul Vernon said in a statement.

So we know we have at least one other man doing the same thing, and it appears he's struck again, he said.

Out of the first six victims of the Slapper, four identified the heavily bearded Moran as their assailant while two others described a different, clean-shaven man, Lieutenant Andrew Neiman said.

Neiman said police were anxious to apprehend the Slapper or Slappers, who he said seemed to be picking unsuspecting victims, often women, at random on the streets of Los Angeles.

They just walk up either from behind or directly toward the victim and without any warning or provocation just haul off and slap or punch the person, either in the stomach or face, and it's quite startling, he said.

The assumption is that it's somebody who is not right in the mind, Neiman said.

Police recommended that pedestrians in the downtown area walk in pairs, avoid texting or talking on phones and create distance from strangers as they walked.