I think that our training is about self liberation, not about tibetain Bodhisatva vow to bring hapiness in a whole world. If we go in hell because of sense attachements it will be worst if we still pure and go to liberation.
But there will be a broblem - remorse about this event "i could save them, i didnt... etc" In anyway it will be a bad vipaka fruition in both cases. And this bad kamma comes from :
- sensual pleasures : i go on events where there is many peoples, joy, fun and sensual happiness - if i will rest at home and practice it would never heppen, and even better, if you dont watch tv/radio/news you will no even know about this horror and your mind will be even more peacefull...
- ill will : i have a gun/knife/something to kill beings - if i havn't possibility to kill someone and save others will not be here...
What is good to do, is not to kill the man who want to kill others, but to sacrifice your life to stop/prevent this man killing or to let a chance to other to escape because you cover them peacefully with 5 khandhas and mind full of compassion - kammic jack pot !!!
Ajahn Nanadassano (before ordaining) : Venerable Ajahn, what is the bigest error that buddhist do in their practice?
Ajahn Jayasaro : They stop practicing ...