An eight-foot cross rests on its side, near an assortment of other crosses and a collection of police uniform patches. Close by are rain-curled posters and hundreds of artificial flowers. “Back the blue,” reads one sign, not far from where stuffed animals sit on a library shelf that once held true crime books.

Here, deep in Dallas’s central library, archivists have spent months sorting more than 10,000 tributes that flowed in after five law enforcement officers were killed in an ambush on July 7, 2016. The collection, one of the largest of its kind, is a staggering chronicle of public grief and support that followed the attack, the first anniversary of which Dallas marked on Friday.

The archive is not about what happened that night, but about “the outpouring of love from the citizens — from the world — that happened afterward,” said Jo Giudice, the director of Dallas’s public library system, told the New York Times. “That’s what’s important.”

In recent years, archivists, historians and librarians have been asked to curate the aftermath of catastrophes: school massacres, a nightclub siege, a bombing, a rampage during a Bible study. The ease and speed with which the sprawling memorials appear belie the years of work that almost always follow.