(CNN) -- The FBI's Ten Most Wanted list now includes a man suspected of killing a young New York mother and her toddler son execution-style in 2010.
Juan Elias Garcia, who the FBI calls an "enthusiastic murderer," now has a $100,000 reward on his head.
"Garcia's callous disregard for human life resulted in the senseless murder of a young mother and her helpless 2-year-old son," said George Venizelos, assistant director in charge of the FBI's New York Field Office, on the agency's website.
Garcia is alleged to be a member of the violent MS-13, or Mara Salvatrucha, gang. He's thought to be hiding in El Salvador.
The FBI said a romantic entanglement and gang rivalries lay at the heart of slayings.
Slaying victim Vanessa Argueta, 19, is said to have had a romantic relationship with Garcia -- and she's also believed to have had ties to two rival gangs: the 18th Street gang and the Latin Kings.
"They were going to kill her for disrespecting the gang," said Special Agent James Lopez in the FBI release. "It is unacceptable for MS-13 members to have girls they associate with be involved with rival gang members."
The FBI said that under the guise of an invitation to dinner in Central Islip, New York, Garcia coerced Argueta and her 2-year-old son into the woods. There, they were met by two co-conspirators -- members of Mara Salvatrucha -- and Argueta was murdered in front of her son. The FBI said the same gun was then used to kill the little boy.
Considered armed and dangerous, Garcia is 5 foot, 4 inches and weighs 125 pounds. He was 17 and answered to the nickname "Cruzito" at the time of the slayings on February 4, 2010.
"His appointment to the FBI's Top Ten list illustrates not only the seriousness of his crimes but our commitment to seeking justice for his victims," said Venizelos.
The FBI requests that anyone with information on Garcia contact its New York Field Office at 212-384-1000, a nearby law enforcement agency or U.S. Embassy or Consulate. People can also submit a tip online.
CNN's Forrest Brown contributed to this report.