SAN DIEGO -- San Diego police were following up on leads Thursday as the search intensified for an unidentified assailant responsible for a fiery four-day crime spree that has left two transient men dead and two others severely injured.
Detectives were working to identify a man believed to be responsible for all four crimes, who was seen in surveillance video taken at a convenience store near where the first victim was found Sunday morning.
San Diego police Capt. David Nisleit said the "very violent person" may be using public transportation and urged riders to keep an eye out.
In the video footage, the dark-haired suspect, who appears to be in his 20s or 30s, is carrying a backpack and wearing dark gloves, light-colored pants, a brown long-sleeve shirt or jacket over a dark undershirt and a green short-billed Greek fisherman-style cap. However, Nisleit said he may have changed his clothing or appearance.
He's suspected of killing 53-year-old Angelo De Nardo of San Diego and setting his body on fire in an open area off Morena Boulevard in Bay Park about 8 a.m. Sunday. An autopsy determined that De Nardo had been killed prior to being set ablaze.
Shortly before 5 a.m. the following day, 61-year-old Manuel Mason was found bleeding from wounds to his upper body near Valley View Casino Center in the Midway district. He remains hospitalized in critical condition.
Less than 90 minutes later, 41-year-old Shawn Longley was found dead at a park on Bacon Street in Ocean Beach, about three miles from the scene of the second assault.
A 23-year-old man was gravely injured in the most recent attack, according to police. His name was not immediately available.
Witnesses told investigators someone was crouched over what they initially thought was a flaming pile of clothing in the area of Broadway and State Street shortly after 5 a.m. Wednesday. After realizing that it actually was a person on fire, a bystander pulled a burning towel off him.
Authorities have declined to disclose the cause or causes of the victims' non-fire-related injuries, but Nisleit said all four victims had suffered significant trauma to their upper bodies.
The attacks prompted city officials to issue a warning to local homeless people to remain vigilant, avoid sleeping alone on the streets and stay in open, well-lit areas.
On Wednesday, San Diego police Chief Shelley Zimmerman told reporters that the series of early-morning attacks against the homeless was her officers' highest priority.
"These evil acts of violence are some of the worst that I have seen in my 34 years in law enforcement," Zimmerman said. "This killer has targeted some of our city's most vulnerable citizens while they are asleep."
San Diego Mayor Kevin Faulconer said police officers were fanning out to make those in the transient community aware of the attacks and to keep them safe.
"These crimes against some of our city's most vulnerable people are absolutely reprehensible," Faulconer said. "SDPD is bringing all of its resources to bear to find the person responsible and seek justice for the victims."
Anyone who spots the suspect was urged to immediately call 911. Anyone with additional information about the suspect or any of the assaults was asked call police at (619) 531-2293.
Anonymous tips can be submitted by calling Crime Stoppers at (888) 580- 8477 or by contacting the agency via email at sdcrimestoppers.org.