Everybody here is discussing the car and the cyclist, but I don't see anybody considering the possibility that the intersection design is unsafe. That there is a stop sign is a pretty bad signal in itself, Not Just Bikes made a video explaining this: https://www.youtube.com/watch?v=42oQN7fy_eM
It's a low traffic 4 way stop sign intersection. Low speed, probably a 25mph speed limit? If you're cycling, this kind of intersection is only dangerous if you fail to yield/stop appropriately to auto traffic. Which seems like might be what happened here, from the description.
17th street in Potrero is relatively quiet but that particular area often has cars coming off the freeway. It can be a maze to get through on bike. I wouldn't rush to make a judgment until we had a dashcam video.