BONNER COUNTY, Idaho --- A second boy has died after a drowning incident while swimming in the Pend Oreille River last week, according to the Bonner County Sheriff’s Office.

Officials said 17-year-old Isaac Glasser was swimming when he began to go under. His mother tried to rescue him, but he was so panicked he began to pull both of them under, BCSO said in a release. The mother was able to swim to shore for help.

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Officials said the 11-year-old brother, Michael, then swam out to help and struggled to stay afloat before drowning at the scene.

Isaac Grasser was taken by helicopter to Kootenai Health. He passed away on Aug. 4, 2017, the Kootenai County Coroner’s Office confirmed. Officials said the cause of death is still under investigation.