Here is an earlier article for those of us who don't know who Kyle Rittenhouse is:
Kenosha Rittenhouse trial victims: These are the 3 men he shot - CNN
Rittenhouse is at some kind of protest carrying a great big automatic weapon, and some suicidal (literally not sarcastically) person throws something at him on camera, then starts chasing him. After being chased, Rittenhouse shoots the pursuer. 2 shots in front, one glancing along the side of his head and one in back.
The prosecution argued that Rittenhouse provoked the action by pointing the gun and could therefore not use the self defense argument. This is what the jury did not accept. They still applied self defense.
Also the pursuer was not some squeaky clean citizen but had a criminal history, and that may have helped uphold the self defense claim.
The shooting alarmed other protestors, two of whom then got shot as follows:
One person tried to grab the gun away from Rittenhouse while holding a skateboard in his other hand.
The third person shot either accidentally or purposely pointed a handgun at Rittenhouse and also got shot.
That's the basic story.