Austrian authorities announced a third arrest made Friday in connection with the foiled conspiracy to attack three now-canceled Taylor Swift concerts, even as disappointed fans charmed Vienna by trading friendship bracelets and singing the pop star’s famous songs in the streets.

The main suspect, a 19-year-old, planned to target onlookers gathered outside Ernst Happel Stadium — up to 30,000 each night, with another 65,000 inside the venue — with knives or homemade explosives during the concert on Thursday or Friday. The suspect hoped to “kill as many people as possible,” authorities said.