Jhon Jairo Velasquez Vasquez, a top hitman for Colombian drug lord Pablo Escobar, has died at the age of 57. Colombia's National Penitentiary and Prison Institute (INPEC) confirmed on Thursday the death of Velasquez, nicknamed "Popeye," who was hospitalized over a month ago for stomach cancer.

Velasquez had been hospitalized since December 31, according to INPEC. Colombian broadcaster RCN reported he was battling the disease for several months and was undergoing chemotherapy.

#ComunicadoDePrensa El INPEC informa que Jhon Jairo Velásquez Vásquez, alias “Popeye” falleció en la madrugada de hoy. pic.twitter.com/acjCv5LN9s — INPEC Colombia (@INPEC_Colombia) February 6, 2020

Velasquez was known as Escobar's right hand man, commanding the drug kingpin's army of hitmen. He confessed to 300 assassinations and claimed he coordinated thousands as part of the infamous Medellin Cartel, according to RCN.

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He was sentenced to 30 years in prison for the assassination of presidential candidate Luis Carlos Galan in 1989. After serving most of his sentence, he was released in 2014 and eventually became a popular YouTube personality. He said he used the YouTube channel to show his reincorporation into society. However, he was captured again in 2018 for being linked to criminal activity.

His life was the subject of television series, including Netflix's "Narcos" and "Surviving Escobar" -- the latter based on a book he wrote.