By ALANNA DURKIN RICHER, ERIC TUCKER and NOMAAN MERCHANT (Associated Press) BOSTON (AP) — A Massachusetts Air National Guardsman accused in the leak of highly classified military documents appeared in court Friday as prosecutors unsealed charges and revealed how billing records and interviews with social media comrades helped pinpoint the suspect. Among the revelations: That the platform Discord provided information that helped lead the FBI to guardsman Jack Teixeira, and that Teixeira used his government computer to search for the word “leak” on the day last week when news media reports revealed that classified documents had been improperly disclosed. President Joe Biden said the government was working to determine “the validity” of the leaked documents.