I think after the bombings older brother spent his day watching tv and browsing the internet while younger brother was going his usual student routine. In the evening he realized they had been identified and they decided to flee, they shot a police officer and i think that's when the older brother realized they were going nowhere and that their shared psychosis was just that, pointless craziness; instead of sticking by his little brother he got into this mess or surrendering, he probably willingly exposed himself to police shots in order to die like the coward he is, leaving his little brother alone...