Dusk and Ashes: Books 1 and 2 of the Sycamore Hollow Trials by Adam Platt

At dawn and dusk, the open sky becomes a killing ground.
Power fails. Cities vanish. Strange phenomena burn anyone caught outside at the edges of daylight. With the radios silent, survivors learn the rules by watching people die.
Mike and Amelia O’Connell turn their secluded home into a refuge. Every newcomer brings another pair of hands—and another mouth to feed. For Mike, being needed offers a way back from the bottle. For Amelia, it means deciding whose safety she can afford to risk.
Nearby, Duggan gathers frightened survivors with promises of protection. Obedience is the price. As his following grows, the Hollow becomes something worth taking.
Keeping their children alive may mean teaching them to kill.