This story includes descriptions of sexual assault and physical violence. This article is co-published with ProPublica, a nonprofit newsroom that investigates abuses of power. Sign up for ProPublica’s Big Story newsletter to receive stories like this one in your inbox as soon as they are published.

The following story, images and video clips contain disturbing material and explicit language. The footage does not include any images of the shooter or gunshot victims. The faces of teachers and students have been blurred out. In some instances, overlapping voices in the videos made exact transcriptions for captions impossible.

Over the last two years, universities across Texas and the rest of the country have worked hard to mitigate the spread of COVID-19 on their campuses with virtual classes, masks and increased cleaning of public spaces.

SAN ANTONIO — The woman wearing a black blouse, jeans and sunglasses resting on top of her head walked toward the dirt road between a waste management company and the train tracks on the city’s outskirts, the place where an employee of a nearby business had found the bodies of dozens of migrants inside a trailer four days earlier.