Rejón Aguilar was born in Campeche, Mexico in 1976. On April 3, 1993, Rejón Aguilar entered the Mexican Army in his home state of Campeche and in 1996 was assigned to Special Forces Airmobile Group (GAFE). In 1997, he was assigned to the Mexico’s Federal Attorney General's Office (PGR) in the cities of Reynosa and Miguel Alemán in Tamaulipas. In 1998 he was assigned to Saltillo, Coahuila. He deserted the army in February 1999 and in March the same year, at the invitation of Arturo Guzmán Decena, known as "The Z1" was integrated into the group of 14 former soldiers who founded The Los Zetas Organization as the armed wing of the Gulf Cartel.
Rejón Aguilar oversaw the paramilitary training of new recruits and then oversaw Gulf Cartel trafficking activities in the state of Coahuila along with Alejandro Treviño Morales. Rejón Aguilar is responsible for multi-ton shipments of marijuana and multi-kilogram shipments of cocaine from Mexico to the United States. In 2004, Rejón Aguilar coordinated a failed raid on the maximum security prison 'El Altiplano', as he attempted to liberate his boss Osiel Cárdenas Guillén. According to government documents, his plan consisted of using 3 helicopters and over 50 Zeta members to liberate Cárdenas Guillén. In 2007 Rejón Aguilar was assigned to the streets of Nuevo Laredo and Miguel Alemán under the command of Miguel Angel Treviño Morales, where he remained until early 2009.
Mexican authorities had posted a $30 million peso ($2.3 million USD) bounty for Rejón Aguilar, while the United States posted in July 2009 a $5 million USD bounty. On July 4, 2011, police captured Rejón in a Mexico City suburb without firing a shot.
Rejón Aguilar was extradited to the United States on 11 September 2012 for drug trafficking and organized crime charges.