They should be standing in front of the tanks, without considering that they will be killed actually. They should be thinking, the cannons will not be fired if they stand there. Allah would decide according to their intentions and Allah knows the best. Still, what He commands us is being cautious:
“Believers! Take your precaution and [either] go forth in companies or go forth all together (to battle).” (An-Nisa/ The Women 4:71)
Opening your chest to bullets is not permitted. We should always take our precaution and inform those people of this command, too.