A transient was set on fire in downtown San Diego on Wednesday morning in the fourth in a series of attacks on homeless men that have left two dead and a third severely injured.

Witnesses saw someone crouched over what they initially thought was a flaming pile of clothing, but it turned out to be a person, in the vicinity of State Street and Broadway shortly after 5 a.m.

Realizing that it actually was a person on fire, one of the bystanders hurried over and pulled a burning towel off the victim, Capt. David Nisleit told reporters. The assaulted man was hospitalized with critical injuries.

Investigators believe that whoever carried out the downtown assault also is responsible for three similar attacks this week.

The body of the first victim, 53-year-old Angelo De Nardo of San Diego, was found in flames in an open area off the 2700 block of Morena Boulevard shortly after 8 a.m. Sunday, according to police. Witnesses to the attack told investigators they saw a man running across nearby Interstate 5, carrying a gas can.

A second homeless man was found bleeding from stab wounds to his upper body in the 3700 block of Greenwood Street, near Valley View Casino Center in the Midway district, shortly before 5 a.m. Monday. He was hospitalized in critical condition, police said.

Less than 90 minutes later, another transient was found dead in the 2500 block of Bacon Street — about three miles from the scene of the second attack, according to police. His name has not been released.

Surveillance cameras at a convenience store near where the first victim was found captured grainy video of a man who has since been named a person of interest in the case.

“This is a priority for the San Diego Police Department and a priority for this city,” Nisleit said. “We need to find this person, this subject is responsible now for four attacks.”

Authorities urged area transients to remain vigilant, avoid sleeping alone on the streets and to stay in open, well lit areas.

Anyone with additional information on the cases was asked to call police at (619) 531-2293. Anonymous tips can be submitted to San Diego Crime Stoppers by calling (888) 580-8477 or emailing sdcrimestoppers.org.

Crime Stoppers is offering a $1,000 reward to anyone with information that leads to an arrest in these cases.

City News Service contributed to this article.

Chris Jennewein is Editor & Publisher of Times of San Diego.