Over time, Vigil became addicted to the rush.
For Vigil, one of the best parts of his job was also the most dangerous.
He describes becoming addicted to the adrenaline rush that came with risky undercover work.
"I started to take more and more chances, which I later had to curb because I knew that if I continued, I would eventually get killed," he says. "You start to crave that adrenaline rush. If days passed where I wasn't working undercover, I got depressed."
Vigil would head into Mexico in an undercover capacity, without backup from the DEA or the Mexican federal government. He would meet with drug traffickers, oftentimes in isolated areas, and arrange to purchase kilos of heroin.
"I would try to get them to deliver to the US side," Vigil says. "If they didn't, then I would bring in the Mexican authorities. But not until the final moment."
Oftentimes, the drug traffickers would pull out weapons and interrogate Vigil, to see if he was undercover. He had to develop a sixth sense in order to pick up physical signs of deception and ill-intent.
"I was able to talk my way out of many, many difficult situations," he told Business Insider. "They will kill you, if they merely suspect you, even if there's no evidence that you are an undercover."