Most brutal and horrific.
The most important thing, "what have we learned from that incident, looking down the history after 53 years?"
1. Unity is the call of the day. Dividing forces must be silenced or at least distanced, isolated.
2. Develop a strategy to secure our own selves and do not be dependent upon external sources.
3. Properly guard any and every gathering.
4. Pray for the hastening of our beloved Imam, our leader, our hope, our soul, our mentor. We are like orphans in his absence. Allah Almighty please please hasten his reappearance.