The vigil was held outside a Los Angeles Police Department station in South L.A., where members of the victim's family joined community leaders to ask for the public's help in finding her killer.
Investigators say Theus was murdered and her body was found along the southbound 110 Freeway on-ramp on Manchester Avenue Jan. 8. Drivers passing by the area saw the body and alerted authorities around 8 a.m., according to the California Highway Patrol.
Family members want justice.
"We're talking about a 16-year-old. We're not talking about an adult. We're talking about a 16-year-old child!" said Lakeshia Barret, the victim's cousin. "She was thrown on the side of the freeway like trash, and she's a child! She meant something to her family."
The investigation in Theus' death is being handled by the CHP and LAPD is assisting.
LAPD Chief Michel Moore is urging the public to come forward with information, saying someone out there knows something about the murder.