LAREDO, TEXAS — Six people were found dead inside a sealed railway car in Laredo, Texas, after boarding a Union Pacific train near Del Rio, Texas, and becoming trapped during the journey. At least one of the six died from hyperthermia, according to the Webb County medical examiner, and investigators believe the other five also likely died from hyperthermia. The six ranged in age from 14 to 56 and were from Mexico or Honduras.

Paul Nixon, a retired teacher and volunteer with Green Valley-Sahuarita Samaritans, described conditions that lead immigrants to seek rail transport. "We've talked to people who have just had brutal on-foot overland travel with so much cartel abuse, so if there was an alternative, it just seems to me that that might be one of the things that people would do," he said. Nixon also described the dangers of the practice. "But people will get into a boxcar and somebody will close the door and just forget that they're there. I mean, that's a death sentence right there."

Hundreds of people die each year in the borderlands of northern Mexico and the southern United States, according to data from Humane Borders, No More Deaths, and Pima County.

Laurie Cantillo, board chair for Humane Borders, hosted a heat-awareness training for about 25 volunteers the day after the deaths in Laredo were reported. Most heat-related deaths in the borderlands occur from May to September, with July as the peak month, according to Cantillo. "What happened in Laredo is the most painful reminder that many of the victims of heat are children, young children." she said at the training. "Heat exposure and dehydration is a horrible way to die. People become confused and their skin becomes parched and dark in color."