New York (CNN) -- Gus Coletti was shaving when he heard a bang on the door of his house on a barrier island in New York.
"Help me! Help me!" a woman pleaded when he opened the door, shaving cream still on his face.
Coletti says he dialed 911 as the woman bolted, tripping halfway down his steep wooden staircase before unsuccessfully seeking help at a neighbor's home.
Now, a year later, Coletti is convinced that the woman he saw that morning was Shannan Gilbert, a prostitute whose disappearance triggered an investigation that led police to discover at least eight bodies on a remote stretch of beach in Long Island. In an interview months ago, however, he said he couldn't be sure it was Gilbert at his door that day.
Police say they suspect a serial killer or killers.
Authorities in New York's Suffolk and Nassau Counties and in New Jersey, along with the FBI, are still searching for Gilbert, a resident of Jersey City, New Jersey.
If Coletti did see Gilbert, he may have been the last person known to have seen her before she vanished. Yet he says it took Suffolk County police four months to question him, an assertion the police deny.
"A missing person detective came in August, was asking about her. I said, 'Where have you been?' " Coletti said.
Investigators in Suffolk County say Coletti gave them a written statement a month after he called 911 to report seeing the woman at his door, but Coletti disputes that.
"They never got a statement from me in June," he says.
Coletti has insisted that he gave police a written statement in December, eight months after he says the woman knocked on his door.
The Suffolk County police also say they have spoken to Coletti several times since last May 1, though they did not specify when those discussions happened.
His account is chilling.
It was about 5 a.m. when Coletti, 75, says he heard a knock on the door of his home on the barrier island hamlet of Oak Beach, New York.
After the woman dashed away from his house, Coletti says, she hid under his boat, elevated and parked on his lawn, as an SUV drove up. Coletti says he walked up to the vehicle and questioned the driver, whom he described a slim Asian man weighing about 150 pounds.
"I went down, and I stopped him, and I said, 'Where do you think you're going?' " recalled Coletti.
The man said he was searching for the woman because she had left a party upset, and he was trying to find her to bring her back to the house, according to Coletti.
"I says, 'I already called the police. Stay right here.' He says, 'Oh, you shouldn't have done that. She's going to be into a lot of trouble.' I says, 'So are you,' " Coletti recalled.
Gilbert dashed from the boat and ran around the corner toward the beach, Coletti said. The driver then pursued her.
Police arrived about 45 minutes later, and Coletti directed them to the road to the beach.
Coletti says a detective showed up in August to ask him about what happened that day. In response to Coletti's "Where have you been?" question, the detective told him he had just received the missing person report from New Jersey.
"New Jersey dropped the ball. He blamed it on New Jersey," Coletti said.
Jersey City Police Department spokesman Lt. Edgar Martinez said, "We have no comment on any ongoing investigation in our jurisdiction. We are investigating a missing person."