Authorities are working to identify the cause of a partial ferry dock collapse on Georgia’s Sapelo Island that turned a day of celebration into tragedy, leaving at least seven dead and six critically injured as crowds gathered for a cultural festival.

The seven people killed Saturday in a gangway collapse on a Georgia barrier island were all in their 70s, except for one woman in her 90s, the coroner said Sunday.

Eyewitness video captured the frenzied moments after a Georgia ferry dock walkway collapsed Saturday, killing seven people. The video, published Monday by The Associated Press, shows people clinging to the broken walkway to keep themselves out of the water.