The crime scene, alongside a busy freeway off-ramp, was shielded from view by dense brush and tangled tree limbs.
The victims — five people shot to death over the weekend at a spot inhabited by the homeless — were known largely by their nicknames or just their first names.
And Southern California's first significant rain of the season may have washed away evidence.
Police in Long Beach are confronted with a baffling murder mystery.
"There is still a demon out there killing innocent people," said Don Morgan, 58, who was friends with the victims. "Satan was here that day."
Three men and two women were found slain Sunday in the seedy neighborhood of warehouses and apartment buildings near the intersection of two freeways. Some of the victims had been shot more than once.
An anonymous tipster called from a pay phone Sunday morning and directed police to the scene. But even the time of the attack is in dispute: Some neighbors reported hearing gunfire, yelling and a car speeding off just after midnight, while the coroner said the crime occurred sometime Saturday afternoon or evening.
Police said Monday that they had no eyewitnesses and no suspects and had yet to establish a motive for the slayings. But neighbors said people would often drop by to do drugs in the shadows underneath the freeway.
Investigators spent 12 hours collecting evidence, removing dozens of bags of trash and belongings from the spot in hopes of finding clues. And they issued a plea for the anonymous caller to come forward in the hope that he had more information.
Gang graffiti was sprayed along a freeway bridge near the crime scene, and a drainage channel appeared to be the only way in and out of the spot.
"We have a tremendous amount of foliage out there," Police Chief Anthony W. Batts said. "It's very tough getting into."
Morgan said he knew the victims only by their first names or nicknames — LV, Vanessa, Cat, Sammy and Fred. They liked to come to the site to party, he said.
Tippi Briggs, a nearby resident, said she had seen an increase in what she suspected was drug activity in the area. "You see people drive up in their nice cars, go in there, then come out after a couple of minutes," she said. "Some are stumbling."
She also said the area had been plagued in recent weeks by a rash of home and car break-ins.
Elsa Neal, who manages an apartment complex close to the scene, said the area was frequented by homeless people and by those who apparently hung out to do drugs. She said the homeless people would sometimes stop by to ask to use her water to clean their cooking utensils and were always polite.
About 10 relatives of one of the victims, 34-year-old Vanessa Malaepule, assembled a shrine on a tattered piece of old carpet, placing a smiling photograph of her atop a bunch of yellow and white flowers. One of her children sprinkled petals around lit candles.
Relatives of Malaepule said she was the mother of six children and was not homeless but liked to hang out at the spot. They said they did not know why.
The impromptu memorial was interrupted by a California Highway Patrol officer who told the family they were too close to the freeway and needed to move along.