The Desperate Hour (2022) on Netflix

Plot summary

Amy Carr, recently widowed, decides to take a personal day from work. She waves goodbye to her daughter Emily, who boards a school bus, then finds her teenage son Noah still in bed, complaining that he is ill. Amy sets out for a jog through the woods, handling routine calls on the smartphone she depends on. Police cars travel hurriedly past her, and a bulletin on her phone reports that all area schools are in lockdown. Amy places call after call to find out what is happening, and the answers point to an active shooter at the high school. Noah is not at home, and his truck is in the school parking lot.