New York police are questioning a man in connection with a series of deadly shootings of Brooklyn business owners of Middle Eastern descent dating back to July, and a law enforcement official says authorities also recovered a gun that may be tied to the case. 

Officials had said they were looking to question a person dubbed "John Doe Duffel Bag," the balding man with a mustache who was seen on surveillance video near the scene of the latest slaying and who was linked to a video in an earlier incident.

The 63-year-old man, described as a person of interest, was picked up in Bay Ridge on Tuesday afternoon and is talking to police, sources tell NBC 4 New York.

A law enforcement official said a Ruger rifle with a sawed-off stock and an improvised combination laser/light attached to its barrel was found early Wednesday in a duffel bag, which authorities say is the same duffel bag seen in the surveillance video at the scene of two slayings. The weapon uses .22 ammunition consistent with ballistics found at each of the three crime scenes connected to the case.

For more visit NBCNewYork.com.

Authorities also found .22 caliber ammunition, three knives -- one of which appeared to have blood on it -- black gloves and women's pantyhose with the legs cut off in the duffel bag, a law enforcement official said. It wasn't immediately clear where the duffel bag was found, but detectives had been attempting to secure search warrants for the man's Staten Island home and his girlfriend's Brooklyn home.

Sources say he is a fabric and garment salesman, and has several prior arrests, including for stalking and burglary in Pennsylvania. 

The latest development comes as authorities search for a possible serial killer who has gunned down three Brooklyn business owners since this summer. Detectives who specialize in hate crimes and FBI analysts who specialize in behavioral analysis joined the case this week, authorities said.

"John Doe Duffel Bag" was seen on surveillance video wearing an overcoat and carrying a black duffel bag near the scene of the latest shooting. NBC 4 New York has learned that the same man was also seen on video near the second shooting in August.

Authorities say two other possible witnesses seen on video have been questioned and released.

The latest victim, 78-year-old Rahmatollah Vahidipour, a Jewish man from Iran, was killed in his women's clothing boutique on Flatbush Avenue Friday.

Also on NBCNewYork.com: Giuliani: MTA Chair Would Make Great NYC Mayor

"The possibility of a bias motive here is something that can't be excluded," Police Commissioner Kelly said.

After the latest killing, detectives discovered the same gun was used in the fatal shootings of two other shopkeepers, as ballistics matched the .22-caliber gun shell casings on all three. On July 6, Mohamed Gebeli, 65, an Egyptian immigrant and a Muslim, was found shot in the back of his shop, Valentino Fashion Inc. On Aug. 6, Isaac Kadare, 59, also Egyptian but Jewish, was shot in the head in his store, Amazing 99 Cent Deal.

There were other similarities, authorities said. The bodies were all partially obscured by clothing or, in one case, a box. The shops all lacked surveillance cameras, and the owners were alone in the store. The locations of the shops are each about 4 miles apart, with addresses that contain the number eight. Money was taken from everyone but Vahidipour, who had $171 in his pocket.

"We're trying to put it together. We're talking to the FBI; we're doing an all-out effort to solve these murders," Kelly said.

Kelly said it's reasonable to think the shooter had canvassed the area to find locations where no cameras existed.  

"Here you have three stores where the proprietor is there by himself, no cameras in any of these," he said. "You'd have to speculate that some sort of reconnaissance was going on before the murders took place."  

The commissioner said no one has been named a suspect and no arrests had been made. 

The killings chilled local shopkeepers.  

"Pretty nerve-wracking that a serial killer is on the loose in Brooklyn. You know it's the third one with the same gun," said Howard Prince, the manager of a business near the She She Boutique.

Prince said police were stressing that no one should work alone.  

"I mean, that's not the part that concerns me," he said. "The part that concerns me is you take somebody's life that's 78 years old for no reason."  

Kelly said city shop owners should be alert and aware of their surroundings and should call police or 911 at the sign of trouble.

The Associated Press contributed to this report.