An Altoona, Pennsylvania, area man will be questioned Monday in connection with the killing of UnitedHealthcare’s CEO in Manhattan last week, in part because he was found with a gun similar to the one used in the shooting, according to two with the Sources familiar with the matter told NBC News.

The sources say it is too early to determine whether his case is related to the death of Brian Thompson, but they are investigating it as a potentially significant development. According to the sources, customers at a local McDonald’s thought he was suspicious and called police. Arriving officers noticed a fake ID and took him in for questioning.

At the police station, the sources said, officers discovered the man had a gun similar to the one used in Thompson’s murder, as well as a silencer and a fake New Jersey ID. The suspected shooter reportedly used a fake New Jersey ID when checking into a Manhattan hostel last month. He may also have taken a bus to get out of New York.

According to the sources, investigators are looking into whether the man interviewed recently got off a bus from Philadelphia. NYPD detectives are on their way to the area to question the man, who sources said looked similar to the suspected shooter.

The development comes as a private funeral for Thompson is taking place on Monday. The 50-year-old manager was shot at close range while on his way to an investor conference at a downtown hotel last Wednesday, according to a source familiar with the site’s plans.

Five days after the shooting – by a man caught on surveillance cameras across Manhattan – the killer remains at large. The largest police department in the country, along with the FBI, are after him as the trail leads investigators to Atlanta. Although they obtained a clear image of his face, among other things, authorities have yet to identify him.

Late Saturday, police released two more photos of the suspected shooter that appeared to be from a camera mounted in a taxi. The first shows him outside the vehicle and the second shows him looking through the partition between the back seat and the front of the cab. In both cases, his face is partially obscured by a blue medical-style mask.

The new photos came after authorities recovered a gray bag in Central Park that may have belonged to the suspect. The bag was taken unopened for forensic examination before investigators examined its contents. Sources later said the bag contained a jacket and Monopoly money, but no gun. DNA testing is underway.

Police have traced the shooter’s steps through surveillance video and apparently left the city by bus shortly after the shooting outside the New York Hilton Midtown on Wednesday morning. He was seen on video about 45 minutes later at a downtown bus station, NYPD Chief of Detectives Joseph Kenny said.

As the high-profile search expanded across state lines, the FBI announced late Friday that it was offering a $50,000 reward for information leading to an arrest and conviction, in addition to the reward of up to $10,000 , which the NYPD has suspended. Police believe the suspect acted alone.

Hundreds of detectives are scouring video footage and social media, reviewing tips from the public and interviewing people who may have information, including Thompson’s family and colleagues, as well as the shooter’s randomly assigned roommates at the Manhattan hostel where he was staying.

Looking for a murderer

Using surveillance cameras on almost every building and block, police were able to track the shooter’s movements.

They know that he ambushed Thompson at 6:44 a.m. as the manager arrived at the Hilton for his company’s annual investor conference, using a 9mm pistol similar to the weapons farmers use to kill animals, without a loud noise to cause. They know that ammunition found near Thompson’s body bore the words “delay,” “denial” and “dumping,” mimicking a phrase used by critics of the insurance industry.

Kenny said the fact that the shooter knew that UnitedHealthcare Group was holding a conference at the hotel and which route Thompson might take to get there suggested he may have been a disgruntled employee or customer.

Investigators know from surveillance video that the shooter fled into Central Park on a bicycle and parked it near 85th Street around 7 a.m.

He then walked a few blocks, got into a taxi and arrived at 7:30 a.m. at the George Washington Bridge bus station, which is near the northern tip of Manhattan and provides commuter service to New Jersey and Greyhound routes to Philadelphia, Boston and Washington.

Investigators don’t know what happened next. They are searching more surveillance videos, but have not yet found any video showing the shooter boarding a bus or leaving the train station.

Police used a video to determine that the shooter had been in the city for 10 days before the shooting. He arrived at Manhattan’s main bus station on a Greyhound bus from Atlanta. However, it is not clear whether he boarded there or at one of about half a dozen stops along the route.

Immediately afterward, he took a taxi near the Hilton and stayed there for about half an hour, Kenny said.

On the evening of his arrival, he took a taxi to the HI New York City Hostel around 11 p.m. There, while talking to a clerk in the lobby, he briefly pulled down his mask and smiled, giving investigators the glimpse they now rely on to identify and catch a killer.

NYPD investigators traveled to Atlanta to coordinate efforts there.