Sophie and her mother, Calli. Photo courtesy of Mark Van Bergh, Smithsonian’s National Zoo.

Sad news from the National Zoo: Sophie, a two-year-old sea lion, was found dead this morning.

According to Zoo officials, Sophie was found dead at the bottom of her pool this morning and, as of now, the cause of death is not yet known, but a necropsy will be performed today to find out more. Zoo keepers say that Sophie’s behavior when they checked in on her last night was normal.

Sophie was born to Calli, one of the Zoo’s other sea lions, at the Pittsburgh Zoo, while their home on the American Trail was being built. She lived on the American Trail with her mother, and two other sea lions, Sidney and Summer.

Sophie, of course, won over the hearts of everyone when she became very concerned after a girl at the National Zoo fell down last year, as well when she famously made friends with a young boy visiting the National Zoo with his family in February.