Could this be the work on a disgruntled employee? Most likely an engineer? Their working conditions I suspect are bad as many has left for greener pastures (Gulf, Emirates and HAECO). And those that left are the good ones (multi ratings). Those that remains are stretched, working long hours.
Or, this could be the work of a mentally disturbed employee (there are quiet a few). MAS, please do something. Complete your investigations quickly, and resolve the matter. Dont wait for the police and other authorities. They're even more stretched and lack manpower.
Good luck in the investigations.