Luis Encarnacion was 7 when he and his sister Mariel, 9, were last seen on September 11, 2011, in Arvin, California. They lived with their mother, Mariela Mendizabal. That night their mother was found at home, fatally stabbed in the neck.

Authorities believe the children’s father, Maico Michael Lopez, abducted Luis and Mariel after the killing. Lopez had recently separated from Mariela and reportedly had a history of instability, including threats of self-harm. Witnesses said they saw Lopez with the children on public transportation in Los Angeles the day after the murder, and investigators believe he then fled with them to Mexico. A federal warrant for unlawful flight to avoid prosecution was issued, and the FBI is offering a reward for information.

Luis and Mariel have not been located and the case remains open. If anyone has information about the children, their whereabouts, or Maico Michael Lopez, please contact the authorities.