Early reports of unfolding events frequently come from extremist and fringe outlets (right or left) because they're not that bothered about fact checking, responsible reporting, legal restrictions etc. They just aim to get the footage out first to drive clicks.
Mainstream media will always be slower because they do have to fact check and comply with codes and the law.
When news like this breaks, it's inevitable that people will want to know and talk about what's going on asap and so it's inevitable that some dodgy sources will be shared.
I don't think this is a huge problem and after all, they're often the same dodgy sources that the mainstream journalists are watching and reporting on.
The trouble comes when mainstream media are then too slow, or when they downplay events, withold information, report dishonestly or with bias. Or don't report at all if they think they can get away with it.
When that happens, people stick with the dodgy sources.