How did the families find out?

Dark question I know, but as far as I recall Danny R's death was confirmed in the paper the next day, I remember a story about the Bernall's being at a Rec center or something as well as the Scott's.

Sue was told by a Swat team member but was officially notified the next day. In the movie Dawn Anna a victims advocate came by Laurens house that evening but on the news they said all unaccounted for students were among the fatalities. I don't know if the victims advocate scene was true to life?

I figure at a certain point in the evening the families knew their loved ones had died even if they were not officially notified.

I always heard that the Danny's parents knew he was dead or at least severely injured because they saw his body on TV before anyone ever notified them.

Yeah, Danny's parents put two and two together after seeing a photo of him laying on the sidewalk.
I'm pretty sure it took up to 24 hours between the time the shooting occurred and when the last family was notified of their child's death.

It's safe to assume that most families knew deep down that they lost someone when their kid didn't come home that night.
I'm sure they still held on to some hope, but after the school was cleared, it wouldn't make sense for someone to still be hiding 12+ hours later.
Even if they were hiding, chances are SWAT would of found them, or they would of came out of hiding when they heard the SWAT team yelling out.

That period of waiting must of been such a dreadful time for them.