Police searching for the suspected killer of UnitedHealthcare CEO Brian Thompson are investigating whether the alleged shooter prepositioned an e-bike close to the scene of the incident 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 Wednesday news conference. The motive remains unknown, police said.

Thompson, 50, was in New York City for the UnitedHealthcare investors conference, which was scheduled to start at 8 a.m. His schedule was widely known, police sources said.

He was shot several times at close range outside the Hilton Hotel — where the conference was being held — at around 6:40 a.m. by the intersection of West 54th Street and Sixth Avenue.

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 linked to the suspect was later recovered, police sources said.

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

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

That footage showed the suspect carrying what appeared to be an e-bike battery.

Investigators are gathering evidence as the search for the suspect continues. The FBI — which has the most sophisticated technology for retrieving usable data from cellphones — is assisting with the investigation, the police sources said.

Police also recovered a water bottle and candy wrapper from the scene of the shooting which they believe are linked to the gunman. Fingerprint and DNA tests on the items are ongoing, law enforcement sources told ABC News.

Detectives believe the gunman is not a professional killer, sources said. Bullet casings found at the scene had the words “deny,” “defend” and “depose” written on them, police sources said.

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

“Brian was an incredibly loving, generous, 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 will be greatly missed.”

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.