I too am generally skeptical of Facebook posts, but this wasn't just some random Facebook user, it was an official post from the Placer County Sheriff's Office. In fact the CBS13 article is simply repeating what the Sherriff's Office had already reported in their Facebook and Twitter posts.
Services like the Internet Archive have a hard time, if they're able to at all, archiving Twitter and Facebook social posts, so having alternate sources is helpful in that regard.
I'm obviously as unsure as anybody of the correctness of this analysis, but I found a source that wasn't Facebook for your alternative: https://sacramento.cbslocal.com/2021/06/16/folsom-lake-plane...