PORT-AU-PRINCE, July 27 (Reuters) - A top security official of slain Haitian President Jovenel Moise was arrested by police on suspicion of involvement in the assassination plot, his lawyer said on Tuesday, as another aide"s apparent account of the event was leaked on social media. Presidential Security Coordinator Jean Laguel Civil was arrested on Monday, lawyer Reynold Georges told Reuters, nearly three weeks after Moise was killed on July 7 in the middle of the night at his private residence in Port-au-Prince by a group of more than 20 mostly Colombian mercenaries. Civil"s arrest followed the earlier detention of another senior member of Moise"s security detail, Dimitri Herard. On Tuesday, a July 10 memo signed by Herard setting out the events of the assassination night was leaked on social media. Reuters could not immediately confirm its authenticity. In the three-page document, Herard said he had received a call for help from Moise at 1:39 a.m. on July 7, whereupon he made for the president"s residence and ordered reinforcements. Herard noted he received word of "many detonations" near Moise"s home and advanced on it with other officials. Near the entrance they were confronted by men dressed in black who ordered them to retreat, saying they were part of an operation by the U.S. Drug Enforcement Administration (DEA), he added. Due to the fact his group was outnumbered and concerned that the men might have the president, Herard"s group retreated. They began planning an assault on their adversaries after learning just after 3 a.m. that the president was dead, he added. In the ensuing battle on the afternoon of July 7, three Colombians were killed, Herard said, also noting in the memo that three police hostages were freed. Many questions remain unanswered over who was behind the assassination and how the killers were able to gain access to the president"s home. Georges told Reuters that Civil is innocent. "The real culprits are those who gave the authorization to these Colombians to enter Haiti; police should arrest them," he said. The U.S. Federal Bureau of Investigation conducted a raid linked to Moise"s assassination in a gated community in Florida, a spokesperson for the agency confirmed on Tuesday after media reports about the incident. "The FBI and (Homeland Security) are conducting court-ordered law enforcement activity in the vicinity of location. The affidavit in support of the search warrant has been sealed by the court," an FBI spokesperson told Reuters in a statement, without giving further details.