nations official. the aleppo offensive by syrian and russian military forces has been the most sustained and intensive aerial bombardment campaign witnessed since the beginning of the conflict more than half a decade ago. the results in human terms have been horrific. aleppo has essentially become a kill zone. reporter: the fact is there are flow angels in this awful grinding five-year war. in the last few days, independent observers have accused both the syrian regime and the rebels of carrying deadly attacks against schools in northern syria. the u.n. saying air strikes against a school near the rebel-held city of idlib killed dozens including 20 children on tuesday. the syrian observatory for rebel rights says artillery killed at least six children in government-controlled aleppo on thursday. and with the rebels latest indiscriminate shelling of western aleppo, the grim death