This happened in Roanoke, which is left leaning. Republicans are going all out to cheat in this election.
Edit: Here is the law on tampering with ballots in Virginia. Class 5 felony
https://law.lis.virginia.gov/vacode/title24.2/chapter10/section24.2-1009/
I’ve always had to sign my vote by mail ballot envelope in CA. They keep a signature on file from when you last registered to absentee (not vote at your polling place) vote and compare the two to see if someone else is trying to vote in your name.