"[7] The state government of Tamaulipas reported that a group of inmates entered a prohibited area inside the prison and attacked the members of their rival gang.
[12] Moreover, in 1991, the time when Juan García Ábrego was the supreme leader of the Gulf Cartel, the federal prison in Matamoros experienced the massacre of 18 people.
[13][14][15] In the nearby border city of Reynosa, Tamaulipas, 21 inmates were killed after a shooting inside the prison on 20 October 2008.
[19] On 19 February 2012, in the city of Apodaca, Nuevo León, 44 were killed and 12 were injured in a prison riot; the brawl was, according to local authorities, between the Gulf Cartel and Los Zetas, their former allies.
[24] In Tijuana, Baja California on 18 September 2008, nearly 19 inmates were killed in a brawl between rival drug cartel members.