People showed up in droves to have a good time at Avicii’s concert at Boston’s TD Garden on Wednesday night, but unfortunately, the night turned out to be exactly the opposite for many. According to CNN, dozens of people — anywhere from 30 to 80 — were hospitalized during the famous DJ’s show.

So what went wrong? Authorities say that many people ended up suffering from dehydration and problems related to drugs and alcohol… and 13 patients who ended up at Massachusetts General Hospital were between the ages of 16 and 19.

“These concerts should be outside,” Chanel Andre, a fan who was at the show, said. “I think it was a combination of heat and drugs, more the latter.”

The “Wake Me Up” producer was upset to learn that so many of his fans had to leave the concert in ambulances, and tweeted after his performance to show his support.

“Just hearing the awful news abt tonight,” he said. “It’s a terrible thing, I rly hope everyone is ok! My thoughts go to those affected & their families.”

Lesson learned: Make sure to stay hydrated when you’re at a concert — or anywhere you expect there to be large groups of people — and maybe lay off the drugs and alcohol before you go… and while you’re there. Everyone needs to stay safe!

Source: CNN, Twitter