They claim he made a threat. The article failed to print his side of the story for some curious reason. It isn’t printing any testimony from the bystanders, either.
Multiple people are still dead because they brought guns into a disagreement over $2.90, but the headline implies a lot more unreasonableness on the individual cops’ parts as opposed to the overall policy.
Cops will often lie about the danger of a suspect in order to justify elevating their use-of-force. That said, they weren’t that concerned by his unreasonableness when they deployed tasers into the crowd first. They didn’t switch to guns until they realized the tasers weren’t going to work.