Here’s a link to local coverage from WTVJ in Miami. The death toll stands at six according to reports.
It could have been a lot worse; Florida International University is on spring break so there was less traffic than normal, and the bridge was still under construction so there were no pedestrians on it at the time. But the road that the bridge crossed, SW 8th Street, also known as Tamiami Trail, is a major east-west artery and is always busy.
(My office is ten miles east of FIU and I heard about it via Facebook. But I marked myself safe just in case.)