According to Boston's WHDH, "At least 80 people have been treated for medical issues at the Avicii concert at the TD Garden" tonight:
"EMS responders on the scene say they have transported people for a series of issues including dehydration, alcohol and drug overdoses."
Check out the video below for the full report:
Update: Avicii just tweeted this message:
Just hearing the awful news abt tonight. Its a terrible thing, I rly hope everyone is ok! My thoughts go to those affected & their families.— Tim Bergling (@Avicii) June 26, 2014