It's 100% true that MAGA people were being very vocal all over social media trying to characterize him as not being a trump supporter. What part of that do you think was a lie?
he’s clearly commenting on how the “maga gang” is characterizing the murderer. There’s no statement directly about the murderer.
How is it false? It isn't making the claim that the shooter was MAGA, but commenting on the right wing influencer sphere's recurring habit of accusing mass shooters of being associated with any group other than themselves.