Held on July 29, 1995, it was Taiwan’s first ever rave. “You know, 30 years ago. It’s like, I can’t believe it,” said Allen Chen (陳宏愷), the rave’s organizer and DJ, interviewed last week by phone.

Investigators say the fight in which Draven Addison, 14, was stabbed to death was captured on cellphone video on the morning ...