Not necessarily, they would only know that "something" happened to Picard. They would have to rely on the info given them by whomever brought Jean-Luc home. Once Picard woke up, they would get his version of what happened. Laris essentially told him that there was nothing available to confirm his version of the story. The Police brought him home and said he was the only one found on the roof. I just watched that scene again (at the 34:00 mark) to get a clearer memory of it. Zhaban says he took a bad knock, but neither of them mention an explosion. Obviously the 'Police' didn't mention that.