A judge sentenced the killer to four life terms, adding to three life terms he already received in a third case.
A prime example: The case of Sage and Isaac Cook, two brothers whom law enforcement recently found in Mexico.
No date has been set for the return of the Texas teenager and his mother from Mexico.
Ethan Couch and his mother were found in a Mexican resort town on Monday night.
Authorities believe Tonya Couch might be with her son, the "affluenza" teen who killed four people in 2013.
Authorities are handling the ongoing case of Michael Cavallari as an active missing person investigation.
The students were "held against their will" over the weekend, police said.
The boy's father has been charged with abduction.
Further studies are needed to determine the cause of death of 14-year-old Avonte Oquendo