. >> reporter: captain stacy holland and his team from the texas department of public safety are trying to stop drug smugglers from crossing from mexico into the u.s. >> right there, right there. one guy's gotten out. >> reporter: they are also trying to stop the violence of a full-scale drug war from spilling north. >> are there parts of this border that you would be basically lawless or run by the cartels? >> absolutely. >> reporter: smack in the middle of this 21st century version of the wild west, two young americans, david hartley and tiffany young, just teenagers when they fell in love. >> we started dating in '98. the summer of '98, and dated for quite a while before we got engaged in 2001 and married in 2002. >> what took so long? >> we were 18. >> reporter: they wound up here, in the mexican border town of reynosa, jut south of mcallen. he was a district manager for an oil company. >> it was a blessing to us and our marriage. yeah. we were -- that's where we truly grew as a couple and had adventures. >> reporter: when the hartley's first arrive here this peaceful town was a per

. >> reporter: captain stacy holland and his team from the texas department of public safety are trying to stop drug smugglers from crossing from mexico into the u.s. >> right there, right there. one guy's gotten out. >> reporter: they are also trying to stop the violence of a full-scale drug war from spilling north. >> are there parts of this border that you would be basically lawless or run by the cartels? >> absolutely. >> reporter: smack in the middle of this 21st century version of the wild west, two young americans, david hartley and tiffany young, just teenagers when they fell in love. >> we started dating in '98. the summer of '98, and dated for quite a while before we got engaged in 2001 and married in 2002. >> what took so long? >> we were 18. >> reporter: they wound up here, in the mexican border town of reynosa, jut south of mcallen. he was a district manager for an oil company. >> it was a blessing to us and our marriage. yeah. we were -- that's where we truly grew as a couple and had adventures. >> reporter: when the hartley's first arrive here this peaceful town was a per

. >> reporter: captain stacy holland and his team from the texas department of public safety are trying to stop drug smugglers from crossing from mexico into the u.s. >> right there, right there. one guy's gotten out. >> reporter: they are also trying to stop the violence of a full-scale drug war from spilling north. >> are there parts of this border that you would be basically lawless or run by the cartels? >> absolutely. >> reporter: smack in the middle of this 21st century version of the wild west, two young americans, david hartley and tiffany young, just teenagers when they fell in love. >> we started dating in '98. the summer of '98, and dated for quite a while before we got engaged in 2001 and married in 2002. >> what took so long? >> we were 18. >> reporter: they wound up here, in the mexican border town of reynosa, jut south of mcallen. he was a district manager for an oil company. >> it was a blessing to us and our marriage. yeah. we were -- that's where we truly grew as a couple and had adventures. >> reporter: when the hartley's first arrive here this peaceful town was a per

these cartels is that they're ruthless and violent, but they're not stupid. >> reporter: captain stacy hollandays that the proof is in these videos, captured night after night by the thermal imaging camera mounted underneath his helicopter. just the last year, in has been more violence and most disturbing to holland, more coordination, lookouts even reconnaissance in the smuggling. >> one thing you have to understand is how well coordinated this is and what the level of scouting and planning and organization is. >> right coming up. >> reporter: these videos of chases at first made to sense. >> yeah. i got it. >> reporter: drug runners caught in the u.s. and then racing back to mexico. >> coming up to the river. >> reporter: their stolen vehicles hurled full speed into the rio grande. >> oh, my god. splash down. >> reporter: at first, law enforcement believed these were desperate attempts to escape. then they began to hear radio traffic. coordinates. >> right there. oh-oh! >> in the water. >> that's a recovery team. >> just a recovery team? recovery team right there. >> reporter: the cartels ev