According to himself, he was born in Albuquerque. His father owns Tampico Furniture on Menaul. He worked in the store before quitting. Walt was a customer back then, and he speculated that he might have met Walt at that time. He has a degree in Business Administration from the University of New Mexico. He originally wanted to study music in Oberlin College or Berklee College, but his father persuaded him not to. He also has an uncle called Alex who wrote songs for the furniture store infomercial.
Sometime after that he began working as a meth distributor with his cousin Emilio Koyama. Unbeknownst to Walter White and Jesse Pinkman, Krazy-8 was a DEA informant, acquiring the customers of the dealers he rats out.
Krazy-8, secretly a snitch to the DEA, reported the location of Emilio and Jesse's meth lab. It led to the bust of the lab and the arrest of Emilio.
When Jesse tried to sell Walt's new product to Krazy-8, he forced Jesse to take him to his new partner. When Emilio recognizes Walt from accompanying Hank on the drug bust, Krazy-8 furiously believes that Walt is involved with law enforcement and plans to kill him until Walt offered to teach him his meth formula.
Emilio and Krazy-8 follow Walt into the RV and force him to show them his recipe at gunpoint. While mixing chemicals, Walt created a small explosion that produces phosphine gas, choking and incapaciatating both Emilio and Krazy-8. Walt explains to Jesse—who tripped and knocked himself unconscious before Krazy-8 and Emilio entered the RV—that one whiff of phosphine gas is enough to kill .
Emilio died as a result of the phosphine gas, but Krazy-8 eventually regained consciousness, prompting Jesse and Walt imprison him in Jesse's basement by securing him to a pole with Jesse's bike lock. Walt and Jesse flip a coin to decide who kills Krazy-8. The coin flip determines that while Jesse is in charge of "disincorporating" Emilio's body, Walt is responsible for killing Krazy-8. However, Krazy-8 lives for several days as a prisoner while Walt worked up the courage to kill him .
Walt attempted to rationalize freeing Krazy-8, who had regained his health. Walt drinks beer with Krazy-8 and gives him food and toilet paper before discovering, in Jesse's kitchen, that Krazy-8 has stolen a shard of broken plate. Walt confronts Krazy-8 about the piece of broken plate, and as Krazy-8 tries to attack him with the shard Walt strangles him to death with the bike lock . It is then heavily implied by Jesse that he was dissolved in hydrofluoric acid like his cousin Emilio.