Emma, Welcome to the HS Baseball Web!
There are many smart umpires here and then some guys like me who pretend.
I won't claim to speak for the umpires, but suspect they'd need a little more information to answer your question.
Rule 7.08 (J) is the rule in question, it reads: He fails to return at once to first base after overrunning or oversliding that base. If he attempts to run to second he is out when tagged. If, after overrunning or oversliding first base he starts toward the dugout, or toward his position, and fails to return to first base at once, he is out, on appeal, when he or the base is tagged;
If you could provide some more details, it would help...
Like did he turn towards second while the firstbaseman had the ball and get tagged out?
Did he simply over run first, turn to the secondbase side but simply return to first?
Was this a HS game or some other level of baseball?