A linear translation of the MT of I Samuel 6:19
וַיַּךְ בְּאַנְשֵׁי בֵית שֶׁמֶשׁ כִּי רָאוּ בַּאֲרוֹן יְהוָה, וַיַּךְ בָּעָם שִׁבְעִים אִישׁ חֲמִשִּׁים אֶלֶף אִישׁ, וַיִּתְאַבְּלוּ הָעָם כִּי הִכָּה יְהוָה בָּעָם מַכָּה גְדוֹלָה
is something like
And [he, God] smote the men of Bet Shemesh because they looked into the ark of YHVH, from the people seventy men fifty thousand men, and the people mourned because YHVH smote the people a great blow.
In the above I use "men" to translate איש and אנשים in order to distinguish it from "people" that I use for עם, although אנשים is not necessarily exclusively referring to males.
In any event the composition of the verse in the MT is not clear.
Given that fifty thousand people would have been a major city at the time and Bet Shemesh wasn't that large a town, and that fifty-thousand does not sound proportionate, it appears that the "fifty thousand" is an elision, possibly from I Samuel 5:9 (NASB):
... and He smote the men of the city, both young and old, [fifty thousand men] so that tumors broke out on them.
Another possible reading of I Samuel 6:19 is that the seventy men are the subject of "smote". This would read:
And [he, God] smote the men of Bet Shemesh because they looked into the ark of YHVH. Seventy men [smote] fifty thousand men and the people mourned because YHVH smote the people a great blow.
This reading might be the preservation a historical memory of an additional defeat at the hands of the Philistines at some point, possibly after the ark of the covenant was taken and the sons of Eli were killed.