Search efforts continue for a fourth day as a girls' summer camp confirms 27 children and staff are dead, with 10 campers and one counsellor unaccounted for.

More than 850 people have been rescued by emergency responders. Many of the stories have been astonishing: A Coast Guard swimmer saved 165 people at the summer camp; a 22-year-old woman was rescued after being swept 20 miles downriver and clinging to a tree overnight; and a young girl was found after floating on a mattress for hours.

Here’s what to know about the deadly flooding, the colossal weather system that drove it in and around Kerr County, Texas, and ongoing efforts to identify victims.