There are no crosses or bouquets marking the spots where three homeless men were brutally slain and a fourth critically injured in San Diego last week, but scorch marks on the ground are visible reminders of a killer who set two victims on fire and remains on the loose.

San Diego police released a sketch of the serial killer responsible for a string of violent attacks on homeless people. — San Diego Police Department

Homicide investigators, expanding their round-the-clock efforts to find the serial killer, have enlisted the help of FBI profilers and released a police sketch of the man who bought a gas can shortly before the first slaying.

Investigators are getting the sketch into the hands of social service providers and advocates who work with the homeless, law agencies around the county and state, and even security guards whose eyes are on the city’s streets, trolleys and businesses.

The simple pencil sketch, produced with help from a store clerk who sold the gas can to the suspect, shows a man with large ears and chin, high cheekbones, a square jaw prominent eyes and a cap.

“We really need the public’s help,” said San Diego police Capt. David Nisleit on Thursday, three days after a prime suspect in the case was released from jail because there was not enough evidence to hold him.

Can you identify this man?

San Diego police have identified this man captured by surveillance cameras as the suspect in a series of attacks on homeless men that have left three dead, one critically hurt. San Diego Police Department — San Diego Police Department

Police ask anyone with information about this man or the attacks is asked to call investigators at (619) 531-2293 or Crime Stoppers anonymously at (888) 580-8477.

He said investigators are following every lead sent in directly to them or through Crime Stoppers’ anonymous tip line. Some tipsters have been sure they had just seen the man whose image was captured on a surveillance camera early last week. None of the leads has panned out, so far.

“This is still the top priority for the San Diego Police Department,” Nisleit said. “It’s our hope and our belief it’s just a matter of the right person seeing the sketch.”

He called the case unique in his 20-years’ experience on the department, and said there is no doubt all four men were attacked by the same hand. He has refused to disclose what type of weapon was used on the victims, each of whom suffered major upper body wounds.

Nisleit said the department asked for the FBI’s help last week in creating a serial-killer profile. Investigators are also searching national records for any similar sprees and have warned California police departments to be on the lookout for crimes that fit the pattern.

“We’re looking for similar cases, methodology,” he said. “We’re looking for previous cases dated to way back, in case a person was released from custody.”

An FBI profile, conducted by its behavioral analysis unit, takes considerable time to produce and is not yet completed, Nisleit said. Noting there have been no new cases in San Diego in eight days, he said one trait of series killings is a “cooling-off” period. But then they typically resume.

Last week, a deputy district attorney told investigators about a 2010 case involving one homeless man who set another on fire in Chula Vista , a source said. That man, Anthony Padgett, was convicted in the case and served a prison term. Based on the prior case and similarities between Padgett’s looks and the man in the surveillance video, police arrested the 36-year-old on July 7 as he walked along Broadway in Chula Vista.

Homicide detectives had been working with county prosecutors before and after the arrest, but by Monday they decided a case against Padgett wouldn’t stick. There was “exculpatory” physical evidence and witness statements that tended to rule out Padgett as the killer, Nisleit said.

He was released from custody within hours of his scheduled arraignment.

Nisleit defended making the fast arrest before all the evidence against Padgett could be confirmed.

“It was a tough decision, one of those damned if you do, damned if you don’t situations,” the captain said. “But we had to ask ourselves, ‘What if you lose him and someone gets killed?’ …The risk was too great.”

He declined to say what Padgett did once freed from jail, but said investigators had a conversation with him regarding his own safety.

ATTACKS ON HOMELESS

The series of violent assaults began July 3, with the death of Angelo De Nardo, 53, who was killed and then set on fire in a greenbelt along a set of railroad tracks near Clairemont Drive and Morena Boulevard. Firefighters doused the flames, which scorched a tree and grass, and discovered his body about 8 a.m.

Angelo De Nardo, 53, was killed and set on fire along a set of railroad tracks near Clairemont Drive and Morena Boulevard on July 3. Police continue to hunt for the killer behind three other attacks on homeless men. Pauline Repard

Investigators later found surveillance video inside a nearby Bay Park gas station market on Clairemont Drive that showed a man who bought a gas can a short time before De Nardo’s body was found. He is shown wearing a green cap with a short visor, similar to a Greek fisherman’s hat. His age was estimated at 35 to 50.

He was called a suspect in the case and his image was released to the public early last week. Meanwhile the attacks continued.

On July 4, about 4:50 a.m., Manuel Nunez Mason, 61, was critically injured on Greenwood Street in the Midway District. Less than two hours later, Shawn Mitchell Longley, 41, was found dead of injuries on Bacon Street in Ocean Beach.

Then, about 5 a.m. on July 5, witnesses heard loud pounding noises and saw one man set another on fire in a grassy spot along a walkway between condominium complexes off State Street and Kettner Boulevard, south of Broadway in downtown San Diego. Investigators said a towel was ignited on top of the critically wounded man, identified as 23-year-old Dionicio Derek Vahidy. A witness grabbed away the towel before the victim was burned.

Vahidy died of his injuries Sunday.

Police said three of the victims were asleep when attacked, and all were off by themselves, away from other transient camps.

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