The police arrested a 20-year-old man Tuesday in connection with the fatal sidewalk attack of a 68-old-man on Friday, the authorities said.

The police said they were holding the suspect, Jamie Pugh, on charges of murder, robbery and assault.

Surveillance video captured the attack, which occurred Friday evening on East Sixth Street. The footage shows a man cornering a smaller man, hurling him against a wall and then stomping on him as he lies crumpled on the ground. The assailant then walks away. Several people pass by the victim, Wen Hui Ruan, a retired garment factory worker, but do not come to his assistance. After several minutes, a woman kneels next to him; the police arrive sometime later.

Mr. Ruan was taken to Bellevue Hospital Center, where he died from his injuries on Saturday.

The Ninth Precinct detective squad, which covers the East Village, received a tip on Tuesday, not long after midnight, that the man they were looking for was in the neighborhood, the police said, adding that Mr. Pugh was taken into custody soon afterward.

Investigators believe that Mr. Pugh had sought to rob Mr. Ruan. In custody, Mr. Pugh did not give a statement to detectives, the police said.

The police have said Mr. Ruan was most likely identified as a vulnerable target for a robbery, but have provided no other details for why he was singled out. Mr. Ruan came to the United States from China 20 years ago. In his retirement he spent much of his free time playing Chinese chess on Mulberry Street. He lived on Avenue C, just around the corner and down the block from where he was attacked.

Mr. Pugh, who lives in a housing development on the Lower East Side that is also near the site of the attack, has been arrested numerous times, on charges that include criminal trespass; most of the cases against him, however, have been sealed.

Relatives of Mr. Pugh could not immediately be reached for comment. The Legal Aid Society, which is representing Mr. Pugh in a prior case, said the judge would assign him a lawyer during his arraignment hearing if he needed one.

One of Mr. Ruan’s daughters, Jenny, declined to speak to a reporter by phone. At a memorial on Monday, she was despondent, dropping to her knees and wailing that she had not been there to help her father: “So many people passed. They didn’t help, they didn’t call the police. Why wasn’t I here when you needed me?”