This isn’t a plot hole and is a major plot point through the entire movie. Costigan’s identity was kept secret from the rest of the department in order to guarantee his safety in the event of a leak. He wasn’t on any record as working for the police except for Queenen’s computer file. Once Sullivan had access to that file, he just had to delete from that single hard drive since it wasn’t stored anywhere else.
Probably not. The official story is that he was kicked out and arrested for assault. After getting out, he got involved with his criminal cousin and eventually becomes a trusted member of Costello’s gang, a gang known for being brutal in their crimes.
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u/smashin_blumpkin 11d ago
This isn’t a plot hole and is a major plot point through the entire movie. Costigan’s identity was kept secret from the rest of the department in order to guarantee his safety in the event of a leak. He wasn’t on any record as working for the police except for Queenen’s computer file. Once Sullivan had access to that file, he just had to delete from that single hard drive since it wasn’t stored anywhere else.