Gilberto Fonseca Carillo (died 1984) was the son of Guadalajara cartel founder Ernesto Fonseca Carrillo.
His father was absent for much his life, but hired Omar to look after him. After leaving a boxing arena, he got into a scuffle with a drunk man after the latter urinated on Gilberto's car. During the fight Gilberto asked Omar to shoot the drunk man, but in the heat of confusion Omar shot Gilberto in the head, killing him instantly.
Ernesto began to appreciate his son much more after his death, and ordered the construction of a mausoleum for his son. He also had his right hand man Sammy Alvarez kill Omar.