How seriously did state and local police take the threat of terrorism on July Fourth? If the experience of Henry Lussier is any indication, the answer is very seriously. Lussier is a longtime member of the Tanglewood Festival Chorus, which performed as part of the festivities on the Esplanade Thursday. Before the concert, the chorus met at Symphony Hall, about a 20-minute walk from Lussier’s home in Central Square. “I’d heard the Mass. Avenue Bridge was closed, but I didn’t think it was closed closed,” said Lussier. The first police officers he encountered let him pass, but he was stopped about halfway across. “I heard someone say, ‘Hey you, get over here,’ ” said Lussier, who was wearing tuxedo pants and a white shirt. “I told him who I was and he said, ‘Sing “God Bless America’’.’ ” Lussier, whose day job is director of marketing for the Lyric Stage Company, complied. “I wasn’t sure if he was kidding, but I didn’t question him,” he said. “A big cop is standing in front of you, you do what you’re told, so I started singing.” The officer was apparently impressed because he gave Lussier a ride to Symphony Hall. . . . A shout-out to longtime Globe photographer Bill Brett, one of six people honored at the Boston Pops July Fourth show for being involved for 40 years. The others were executive producer David Mugar, operation coordinator Brian Kerins, Pops cellist Toni Rapier, Cambridge public safety liaison Jack Bakey, and Pops librarian Bill Shisler.