The interrogation of the criminals had begun, but it might take a long time to get the results, especially since the Thule Society was backing them, with plenty of power and wealth to fight legal battles.
However, these five people were all armed, resisting arrest, and illegally possessing firearms. So they would have to spend at least one or two years in prison without the possibility of parole or release due to illness. Not to mention the involvement in a murder case with conclusive evidence, it wouldn't be easy to get away.
More importantly, the chairman of the Golden Dawn had specifically called Leonard Ethan to let them intervene in this matter, trying to reduce the Thule Society's interference with the local judiciary as much as possible to allow the court to make a fair judgment.