Police are reportedly questioning a man in Pennsylvania in connection with the New York City shooting death of the UnitedHealthcare CEO, Brian Thompson.

NBC New York reported that the man being questioned on Monday was in or around Altoona, Pennsylvania – and had been found with a gun similar the one used in Thompson’s killing.

Monday’s development came after police on Sunday again searched a Central Park lake for evidence – including the murder weapon – connected to the Midtown shooting.

As the search for the executive’s killer entered its sixth day on Monday, officials have said they are widening their search.

Law enforcement sources told CBS News that the New York police department and the US marshals had sent investigators to Atlanta to make inquiries and review surveillance footage from Greyhound bus stops on the route from Georgia.

Police have not named a suspect. But Eric Adams, New York’s mayor, hinted on Sunday that authorities may be getting closer to publicly identifying the man in photographs released to the public.

“The net is tightening and we’re going to bring this person to justice,” Adams said on Saturday.

“We don’t want to release that now. If you do, you are basically giving a tip to the person we are find … we’re seeking, and we do not want to give him an upper hand at all. Let him continue to believe he can hide behind the mask.”

Two additional images were also released of a masked man in the back of and outside a taxi he used to soon after Thompson was fatally shot outside a midtown hotel the morning of 4 December.

Only one photograph of the suspect without a mask has been made public: an image taken at a hostel soon before the murder when he apparently dropped the mask at the request of a front desk employee.

According to CBS, NYPD divers searched Central Park’s lake on Sunday after failing to recover anything from a similar underwater drag a day earlier. That came after a backpack containing a jacket and Monopoly money that is believed to be the Thompson murder suspect’s was found in the park.

The retired NYPD officer Tom Walsh told the outlet it made sense that police would continue searching the park for clues – and especially for the murder weapon – in the absence of concrete evidence.

“They found the backpack here in Central Park, so it only makes sense that that’s a good dumping ground for a gun,” Walsh said.

Though his survivors include a widow and two sons aged 16 and 19, Thompson’s death elicited a grim schadenfreude from many in the US who had been mistreated by the country’s rapacious health insurance industry. A private funeral for Thompson was planned for Monday, NBC New York reported.