This situation came up in a game toady. The batter swung and missed the ball for a strike. The catcher caught the ball on a bounce and threw to first base where the runner had legally left the base toward second but was tagged by the first baseman as he returned to first but had not yet touched the base.
Is the runner out? Or, is the play dead when the catcher caught the ball after the missed swing? Your thoughts please and, if there is one, the rule covering this situation. Thank you.

See rule 7.4B For each legally pitched ball swung at and missed by the batter.
EFFEXT: DEAD BALL

Nice play by the catcher, way to be in the game. Except for one thing, in senior softball there is no stealing, therefore no play can be made. DEAD BALL!

To my knowledge, in all of senior softball any swing and miss by the batter is a dead ball.
However in ISA men's ball (not senior) that would be a legal play