Police detectives on Monday were investigating the circumstances surrounding the death of a teenager in Santa Monica.

Santa Monica police responded to the 1300 block of 16th Street shortly after 5 a.m. Sunday after a report of an unconscious victim lying on the ground with a head injury, police said in a statement.

The victim, identified by the coroner's office as 18-year-old Juan Castillo, was pronounced dead at the scene. Castillo had a gunshot wound to the head, Santa Monica police Lt. Saul Rodriguez said.

Detectives are investigating a possible link to an earlier radio call for service, authorities said. At about 12:45 a.m., police responded to the 2100 block of Pico Boulevard regarding a possible shooting.

Officers found evidence of a shooting, police said, but no victims or suspects were located.

"We have not made that link yet, but we have not ruled it out at this point," Rodriguez said. "Beyond that, we are still looking for any possible witnesses who may have seen the crime or seen the individual, our victim, being dropped off — or how he got there."

A man who identified himself as Castillo's father told KNBC-TV that his son had been on his way home from a party when the shooting happened.

"I just want justice to be served," Jorge Castillo told the TV station.

Police asked anyone with additional information concerning the case to call 310-458-8491.