Dynasty Alexander's body was found near an orchard at around 5 pm Sunday, just outside Tulare city limits and not far from Elk Bayou Park.
Tulare Police initially responded, but handed the investigation over to the Tulare County Sheriff's Office, and detectives worked through the night to investigate the homicide.
Lt. Joe Torres from the Tulare County Sheriff's Office says Alexander had visible trauma to her upper body, adding, "There are obvious signs of foul play."
Detectives believe Alexander was killed between approximately 5 am and 5 pm.
Tulare City Councilman Carlton Jones is Alexander's cousin. He told Action News that she was dealing with some personal challenges, but that she had a big family that loved her.
"She was a baby. She just turned 18 years old. It's just a sad place that our world is coming to when there's so many kids that need help, and adults are hurting them instead of helping them."
Jones says the family appreciates the support they've received from the local community and the hard work of Tulare County Sheriff's detectives.
"My little cousin lost her life, but if he's still out there, that means there are other kids who are still in danger, so the faster we catch him, and the faster we bring him to justice, the faster we can have peace."
The search is on for suspects, and Torres says they've already received many phone calls, but hopes they get more.
They're asking anyone who was at Elk Bayou Park on Sunday and noticed anything odd to call them.
"We know somebody out there knows who she was with, and why she ended up being killed," said Lt. Torres.
An autopsy is scheduled for Tuesday.