People were killed by militants when they [People] were gathered for meeting.
Is using were gathered is makes above sentence passive voice?
If yes, then can we imagine that there is any agent/doer who gathered people?
As per my knowledge we need to use had gathered as first action is gathered and the killing.
Also, gathered is intransitive verb. So in above sentence does it conveys the meaning that people gathered there for meeting or the they were asked to gather by someone?
People were gathered for meeting by leader and then he started his speech.