KYIV, Ukraine (AP) – A Ukrainian court sentenced a captured Russian soldier to the maximum penalty of life in prison for killing a civilian, and the Kremlin hinted that it may put on trial some of the fighters who surrendered at Mariupol’s steelworks. Meanwhile, a veteran Kremlin diplomat resigned and sent a scathing letter Monday to foreign colleagues in which he said he had never been so ashamed of his country as when the invasion was launched on Feb. 24. It was a rare public expression of opposition to the war from the ranks of the Russian elite. Heavy fighting was raging in the Donbas in the east, where Moscow’s forces have stepped up their bombardment.