"Women, accompanied or not, literally ran a 'gauntlet' through masses of heavily intoxicated men that words cannot describe," the official wrote.
The report contradicts the Cologne police department's initial depiction of the night as "relaxed," a description that has since been recanted. Authorities now say that more than 100 women have filed criminal complaints of sexual assault — including two reported rapes — or thefts during the festivities that evening, according to the Associated Press.
Roughly 1,000 men described by officials as being largely of "Arab or North African origin" had congregated in the square outside Cologne station that night, with groups reportedly breaking off to assault women. Victims described a sense of lawlessness that evening as criminals flouted the law even with police present.
"They grabbed our arms... pushed our clothes away, and tried to get between our legs or I don't know where," one victim told the BBC News.
Another said attackers put a firecracker in her hood as they stole her phone.
"I heard a sizzling sound in my hood and I somehow tried to get it out of the hood," she said. "Then it fell into my jacket and burned everything. The scars will stay. I was lucky that it didn't explode."
The report obtained by Der Spiegel seemed to corroborate the sense that the attackers, repeatedly described as groups of male migrants, felt that they had the run of areas in front of and inside the train station.
The report describes officers encountering crying, frightened pedestrians, many of them women and girls. Officers reported that their orders were ignored, that they were "bombarded with fireworks and pelted with glass bottles," and that witnesses were threatened when they named the perpetrators, according to Der Spiegel.
The author of the report noted a level of disrespect for police "like I have never experienced in my 29 years of public service."
Cologne was not the only European city to see trouble on New Year's Eve.
Police in Helsinki, Finland said that 15 Iraqi asylum seekers were taken into custody amid allegations of groping and harassing women near the city's central railway station on New Year's Eve. Ilkka Koskimäki, Deputy Police Chief of the Helsinki Police Department, said three women had filed complaints, alleging they had been kissed and touched against their will.
The situation, he said, might have been worse had police not received a tip that groups of Iraqi asylum seekers were planning disturbances that night, leading the Helsinki police to deploy far more officers than usual.
Attacks were reported elsewhere in Germany, too, including in Hamburg and Stuttgart, according to the BBC.
Cologne, however, saw the largest wave of assaults. Due to the overwhelming number of attacks, officials have few leads on the attackers, according to the report. "Security forces were unable to get all of the incidents, assaults, crimes, etc. under control. There were simply too many happening at the same time," its author writes.
Authorities have, however, described the men as being largely of "Arab or North African origin." According to the report, at least one officer quoted a man as saying: "I'm a Syrian! You have to treat me kindly! Mrs. Merkel invited me."
Germany took in a record 1.1 million asylum-seekers last year, driven largely by migrants from Syria. Officials have warned against blaming all refugees for the New Year's Eve incidents, but added that deportation is on the table for any asylum-seekers found to be involved.
"We must examine again and again whether we have already done what is necessary in terms of ... deportations from Germany in order to send clear signals to those who are not prepared to abide by our legal order,” German Chancellor Angela Merkel said Thursday, according to the Associated Press.
She also described the assaults as "repugnant."
“The feeling women had in this case of being at people’s mercy, without any protection, is intolerable for me personally as well,” she said. “And so it is important for everything that happened there to be put on the table.”
Women in Germany have protested the lackluster official response to the attacks, including the suggestion by Cologne's female mayor that women follow a "code of conduct" and approach strangers with caution.
Anthony Faiola and Stephanie Kirchner contributed.