MATAMOROS, Mexico (AP) — Migrants attempting to cross the U.S.-Mexico border often arrive with little more than the clothes on their backs.

But the few belongings they bring often include evidence intended to help them seek asylum, including audio recordings, crime-scene photos, police paperwork and even medical examiner records.

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Immigrant families hope these documents help demonstrate to U.S. authorities the dangers they are trying to escape back home.

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For instance, an MS-13 gang member left eight voicemails on Brenda Mendez’s cellphone. He demanded that she turn over her teenage boy and threatened to dismember both her sons if she refused.

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The family soon fled Guatemala for the United States. They were careful to bring along the voicemails and a copy of the police report Mendez filed against the gang member.