Populating Cells via Data Validation

i have a list of municipalities

Municipalities (this are my choices on my data validation)
aaa
bbb

List of brgys under municipalities

under municipality of aaa
i have brgys
111
112
113
114
115
116

and under municipality of bbb
i have brgys
221
222
223
224
225
226

on a1 = dropdown (aaa/bbb)

when i choose aaa

a2:a7 will populate with brgys under municipality aaa.
please i need help.. already tried this formula =IF(ROWS(A$2:A2)<=COUNTA(INDIRECT(A$1)),INDIRECT(A$1),"")
but the data must also in the same row as the expected result. if there is another way by using vlookup or match formula.
my data must be in another sheet. thank you in advance! Book1.xlsx

how about using vlookup? is there another way? without using this format.

my data for bgys must be on sheet 2. i dont know how to do it.

please help me how to do this using vlookup. thank you

because what if my data was not in the same row and column as the list of values. it will show #VALUE! results.

That should do it. Thanks!