What was going on with all those sirens on Delaware Ave at 2 AM?

I live near Delaware and Summer Street, and last night around 2 AM something woke me up — a long convoy of what sounded like six or seven firetrucks absolutely flying north up Delaware toward Elmwood Village. Loud enough to rattle my windows.

I've been checking the news all morning and can't find a single thing about a fire or major incident. Didn't smell smoke either, which made it even weirder.

Did anyone else hear it? Does anyone know what actually happened? I'm not worried about the sound — I just want to know if everyone is okay and why a response that big didn't make any news.