I don't believe this is true. Can you like anything on BlackLivesMatter.com that touches on Daniel Shaver's death?
https://www.commondreams.org/news/2017/12/09/black-lives-mat...
https://www.facebook.com/JusticeForDaniel/photos/i-just-want...
| BlackLivesMatter.com
The movement is so much more than that website. There's also a big difference between black lives matter and Black Lives Matter.
The website is not the movement.
Second, both of those "opinion pieces" have references to high profile black lives matter activists (deray, shaun king, etc) speaking out about Daniel Shaver, so that's about as official as you're going to get.
Third, that "facebook post" documents an actual event organized by the family of Daniel Shaver, thanking the local blm chapter for their support.
If you have a more substantial voice that has done more than blm in bringing attention to this issue in a productive way, feel free to bring that forward.
Literally the only substantial voice that stood up and went to bat for Daniel Shaver was BLM. You're right, police violence is far from isolated to Black people. Most BLM activists would agree that stopping police violence has multi-racial benefits!