After deadly floodwaters swept through Central Texas, there are questions about the timeline of weather alerts and possible gaps in the warning system.

Kerr County, Texas, lacked a “last mile” warning mechanism that could have saved residents before the deadly floods devastated the area, including a children’s summer camp, killing more than 80 people.

The National Weather Service began sending flash flood warnings that should have triggered cellphone alerts a little after 1 a.m., while local officials began posting on Facebook about four hours later.