A leader of a Mexican fuel-theft gang was shot to death at a hospital where he was undergoing plastic surgery to change his appearance, authorities said Thursday.

Puebla state prosecutors said Jesus Martin, a woman and two other men were killed at the hospital Monday, apparently by members of his own gang, reports the Associated Press.

The killing comes amid an upsurge in bloodshed involving pipeline thieves in the state, where at least 16 people have been slain this week in apparent disputes between gangs.

The most recent killings claimed four victims on a rural road Tuesday in Palmar de Bravo, a township known as a centre for fuel thieves.

Fuel thieves drill an average of 28 illegal pipeline taps every day in Mexico. State authorities have said the gang fighting has occurred in part because a police crackdown that has made it harder to steal fuel.

The main suspect in Martin’s killing has also been implicated in the slayings of five people in the town of Tlaltenango, in a vacant lot that apparently served as a base for fuel thieves, officials said.

Prosecutors also said that Martin had tried to have his fingerprints removed and that doctors at the hospital in the state capital were being investigated for possible complicity.

High-profile Mexican criminal figures have been drawn to plastic surgery in the past.

In 1997, drug lord Amado Carrillo Fuentes died while having plastic surgery to change his appearance. His associates suspected the doctors intentionally caused his death. Sinaloa cartel chief Joaquin ‘El Chapo’ Guzman was believed to have gotten male-enhancement surgery while on the run in late 2015. Guzman was recaptured in January 2016 and extradited to the US in January 2017.