Police searching for the suspected killer of UnitedHealthcare CEO Brian Thompson are investigating whether the suspected shooter placed an e-bike near the scene of the accident as a means of escape, police sources told ABC News.

A masked gunman carried out a “brazen, targeted attack” that was “premeditated,” NYPD Commissioner Jessica Tisch said at a news conference Wednesday. The motive remains unknown, police said.

Thompson, 50, was in New York City for UnitedHealthcare’s investor conference, which was scheduled to begin at 8 a.m. His schedule was widely known, police sources said.

He was shot several times at close range around 6:40 a.m. at the intersection of West 54th Street and Sixth Avenue in front of the Hilton Hotel where the conference was taking place.

The suspect, who was caught on surveillance cameras before, during and immediately after the shooting, had been lying in wait near the hotel.

After the shooting, he fled on foot into an alley, where a phone believed to be connected to the suspect was later found, police sources said.

The suspect then fled on a bicycle and was last seen riding into Central Park at 6:48 a.m., police said.

The gunman was captured on surveillance video at 5 a.m. the morning of the shooting outside the Frederick Douglass Houses, a public housing project on the Upper West Side, sources told ABC News.

These images showed the suspect appearing to be carrying an e-bike battery.

As the search for the suspect continues, investigators are collecting evidence. The FBI – which has the most advanced technology for retrieving actionable data from cellphones – is assisting in the investigation, police sources said.

Police also recovered a water bottle and a candy wrapper from the scene that they believe are linked to the shooter. Fingerprinting and DNA testing of the items is ongoing, law enforcement sources told ABC News.

Investigators believe the shooter is not a professional killer, sources said. According to police, the words “deny,” “defend,” and “deposit” were written on the bullet casings found at the crime scene.

Thompson’s wife, Paulette Thompson, said in a statement that she was “shocked” by the “senseless murder.”

“Brian was an incredibly loving, generous and talented man who truly lived life to the fullest and touched so many lives,” she said. “Most importantly, Brian was an incredibly loving father to our two sons and we miss him dearly.”

Police urge the public to call Crime Stoppers at 1-800-577-TIPS with any information.

ABC News’ Mark Crudele and Josh Margolin contributed to this report.