By Kiet Do

SAN FRANCISCO (CBS SF) — A South Bay high school is mourning the death of a popular student after the plane she was in crashed in a remote area of Santa Clara County.

Judging from the outpouring of emotion on social media, Kiely Vaca was a well-liked senior at Lincoln High School.

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Friends and family started the hashtag #RIPKiely, posting photos and expressing shock and disbelief.

Vaca was on board the Cessna 140 with her grandfather when it went down Saturday night in the back hills of Gilroy.

The Federal Aviation Administration says the cause of the  crash is unknown. The pilot, 69-year-old John Richard from Gilroy, was flying from Frazier Lake Air Park in Hollister to Watsonville.

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The flag in Hollister was flying at half staff to honor the pilot who flew there for many years.

“To hear this happened, it always takes you aback,” said Kevin Brown, a fellow pilot. “And then to hear the news that a younger person was on board — it’s very heartfelt for us.”

The National Transportation Safety Board has taken over the investigation.

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