PENNSYLVANIA (NYTIMES) - A week after a man was charged with raping a woman on a train outside Philadelphia, the local prosecutor cast doubts on initial accounts given by law enforcement authorities that other passengers had been "callously sitting there" as the assault happened.

"There is a narrative out there that people sat on the El train and watched this transpire and took videos of it for their own gratification," the prosecutor, District Attorney Jack Stollsteimer of Delaware County, said at a news conference Thursday (Oct 22). "That is simply not true. It did not happen."

The early characterisation was countered by security video, Stollsteimer said, although he acknowledged that only one person had come forward to describe what happened that night, leaving much about the witness response to the assault unknown.

Over the weekend, law enforcement officials announced the arrest of Fiston Ngoy, 35, who was charged with sexually assaulting and raping a passenger on a train traveling from Philadelphia to its suburbs Oct 13. Among the most egregious aspects of the crime, officials said, was that fellow passengers saw the attack and did nothing, some even filming it on their phones.

"I'm appalled by those who did nothing to help this woman," Timothy Bernhardt, superintendent of the Upper Darby Township Police Department, said Sunday. "Anybody that was on that train has to look in the mirror and ask why they didn't intervene or why they didn't do something."

But on Thursday, with Bernhardt standing at his side, Stollsteimer described that narrative as "misinformation" that was scaring off potential witnesses. He emphasized that there was no law in Pennsylvania that would allow the prosecution of witnesses "for failure to intervene" and further argued that it was a mischaracterization of what had happened.

"People in this region are not in my experience, so inhuman - callous human beings that they're going to sit there and just watch this happen," said Stollsteimer, whose father worked for Septa, as the Southeastern Pennsylvania Transportation Authority is called, and was once the supervisor of the terminal where Ngoy was arrested.

According to an affidavit of probable cause, Ngoy boarded the train at 9:16 pm and sat down next to the woman, who had just boarded as well. Within minutes, the affidavit said, he began trying to grope her as she continuously pushed him away.

The affidavit is vague about what took place over the next half-hour but says that at 9:52 pm, Ngoy removed the woman's pants and his own and began raping her. A transit officer entered the car about six minutes later and pulled Ngoy off the woman, who was taken to a hospital.

Officials have said there were about 10 people in the car when the rape occurred. It was unclear whether the woman made signals of distress that could be seen or heard by others; among the charges Ngoy is facing are counts of raping an unconscious person.

The district attorney declined to characterize the circumstances of the crime but did say it was "not necessarily true that any one person who's getting on the train is going to know exactly what's going on." This was why, he said, authorities were seeking more witnesses.

"Two people, we think, may have actually videotaped, using their telephones," Stollsteimer said. One of those videos was turned over to law enforcement, and one of the people taking the videos, he said, "probably was the one who made the anonymous tip that alerted the Septa Police Department."

This seems to diverge from earlier official accounts, in which it was an off-duty Septa employee who had been on the train and alerted dispatch to what a Septa spokesperson described as "inappropriate activity." Stollsteimer blamed the narrative on the news media and at one point on Septa officials.

"We stand by what we said before," said Andrew Busch, a spokesperson for Septa. "We really want to come out of this highlighting the need for people to call if they see something that doesn't look right." After the news conference Thursday, Bernhardt also stood by his earlier remarks.

"What I committed to at the time, and commit to now, is that there were people getting in and getting off that I thought could have intervened and done something," he said. "Now that doesn't mean they were sitting there filming it, but as the district attorney said, there were plenty of people getting on and off that witnessed it. Now what they witnessed or what they thought, I don't know, because we haven't been able to speak with them."

Ngoy, who is being held at the Delaware County Jail in lieu of US$180,000 (S$242,410) bail, has a record of arrests, including a conviction of misdemeanor assault for grabbing women.

A native of the Democratic Republic of Congo, according to court records, he has overstayed a US student visa and fought past attempts at deportation.

A public defender in Delaware County acknowledged that Ngoy was a client but declined to comment further.