Katie Stack had just joined a marathon running club, following in the footsteps of her older sister. She loved gymnastics and was forever practicing her splits in her Newton backyard. She was a natural at math, had a soft spot for children, and dreamed of one day becoming a pediatric oncologist.
“Katie was a very, very sweet and kind and sensitive soul,” said her mother, Tiffany Stack.
But Stack, 15, also struggled with depression, her mother said. The Newton South High School sophomore took her own life Wednesday. Tiffany Stack has started an online fund in her daughter’s name. Stack’s death came less than two weeks after Newton North High School student Karen Douglas, 18, also took her own life. Full story for BostonGlobe.com subscribers.