The women were attacked in a spree of violence in Manhattan on Sunday. A guard at the library where the man was arrested said he had been a frequent visitor.

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A 28-year-old man was arrested and charged with hate crimes Wednesday evening in connection with a two-hour spree of attacks on women of Asian descent in Manhattan over the weekend, another example of a grim wave of violence against Asian Americans.

There was no indication that the assailant knew any of the seven victims, two of whom were treated at local hospitals. The police charged the man, Steven Zajonc, with seven counts of assault and attempted assault classified as hate crimes, as well as with seven counts of aggravated harassment and harassment.

Mr. Zajonc, whose address was listed as a Midtown drop-in shelter, was taken into custody at a public library on Wednesday, a police spokesman said. The police said Mr. Zajonc, who is originally from Florida, declined to make a statement after his arrest.

The New York Public Library said that guards at the Stavros Niarchos Foundation Library on 40th Street and Fifth Avenue had recognized the man as a regular and had alerted the police. Iris Weinshall, its chief operating officer, said in a statement on Thursday that the guards had a challenging job and that the library was “so proud (but not surprised) of their quick thinking and good work.”

The first attack took place at about 6:30 p.m. on Sunday around East 30th Street and Madison Avenue, about a half-mile southeast of the library, when an assailant approached a 57-year-old woman and, without uttering a word, punched her in the face, the police said. Ten minutes later and a block west, the nightmare repeated itself. The second victim was 25.

The attacks all followed the same template as he made his way south. The next two victims, punched in the face just minutes apart, were also in their early 20s. At 7:05 p.m., a 19-year-old was elbowed in the face at Union Square. Twenty minutes later, the man was on East Houston Street near Mott Street, where he elbowed another woman in the mouth.

The man then headed north to Greenwich Village. The last attack occurred near Eighth Street and Broadway, close to New York University, at about 8:40 p.m. The victim, 20, was shoved to the ground before the attacker fled west.

“There was no prior interaction, and no statements were made” in any of the incidents, the police said. The man’s image was captured by surveillance cameras on Sunday in several locations.

Lt. Elmirel Cephas, a guard who has worked for the library system for 22 years, said in a phone interview that he had seen Mr. Zajonc in the library in recent months, often six or seven days a week from opening to closing time. He kept to himself and did not cause trouble, Lieutenant Cephas said, though he would often spend a lot of time in the restroom, where he would wash up and change into slippers.

Another guard, Roshanta Williams, had seen the man’s image on the news, and she alerted Lieutenant Cephas before the library opened on Wednesday. A couple of hours later, the man walked into the library, and Lieutenant Cephas tracked his movements and then called 911.

“I was definitely surprised that it was him,” Lieutenant Cephas said of the man, who he said normally spent all day sitting quietly on the first-floor mezzanine.

Anti-Asian violence in the city has soared during the pandemic; the police recorded 131 bias incidents against Asians in 2021, up from 28 in 2020 and just three in 2019. Activists caution that incidents are not always reported to the police or classified as hate crimes, making it difficult to capture the true extent to which Asians are being targeted.

Attacks against Asian New Yorkers have recently led to four deaths. Yao Pan Ma, a Chinese immigrant, was beaten as he collected cans in East Harlem in April and died from his injuries on New Year’s Eve. Michelle Alyssa Go was pushed to her death at the Times Square subway station in January. Last month, Christina Yuna Lee was fatally stabbed by a man who followed her into her Chinatown apartment. And GuiYing Ma, who was attacked as she swept a sidewalk in the Corona neighborhood of Queens in November, died of her injuries last week.

Other recent examples of assaults abound, including one that targeted a Korean diplomat and another involving an Asian American performer who was on his way to a preview performance of “The Chinese Lady” by the Ma-Yi Theater Company and the Public Theater.

In a statement last week, the artistic directors of the two companies, Ralph B. Peña and Oskar Eustis, wrote that the performer’s glasses had been broken, his eye had been bruised and he had been kicked several times.

“We are sharing this because the attack on this Asian American artist, which happened near Seward Park not far from where Christina Yuna Lee was tragically murdered, is another incident in a long history of violence against Asian Americans,” they said. “The violence and the hatred that fuels it remain disgusting and heartbreaking and have created an environment full of fear where safety seems scarce for our Asian American neighbors.”

A police spokesman said that the attack on the diplomat was being investigated as a hate crime and that the attack on the performer, who is 16, had been classified as a harassment complaint.

Nationwide, Stop AAPI Hate, a coalition of community and academic organizations, tracked more than 10,300 attacks and other incidents targeting Asian Americans and Pacific Islanders from March 2020 to September 2021. Surveys have also shown that large numbers of Asian Americans are fearful of attacks and harassment, impeding the slow return to normalcy as the pandemic ebbs.

City Councilwoman Carlina Rivera, who represents the district where nearly all of the attacks on Sunday took place, said in a statement that she was “equal parts devastated and enraged” about them.

“Condemnation is not enough,” she said.