FBI Homing in On Brian Thompson Assassin, Raid Where Shooter Was Staying in New York

Detectives are zeroing in on the suspect who brazenly gunned down UnitedHealthcare CEO Brian Thompson outside a Manhattan hotel before fleeing on a bicycle, as FBI raid a youth hostel in search of the alleged shooter.

The NYPD has conducted a search of a youth hostel on the Upper West Side, where the suspected shooter is believed to have stayed, according to the New York Post.

It remains unclear what, if anything, was found during the search.

The masked gunman ambushed Thompson, 50, early Wednesday morning, shooting him multiple times at close range outside the Hilton Hotel where he was attending a conference, sources said.

"This brazen, targeted attack was premeditated," said NYPD Commissioner Jessica Tisch.

Investigators do not believe the assailant is a professional killer, but the motive remains unclear. Bullet casings recovered at the scene bore the words "deny," "defend," and "depose," sources said, according to ABC11.

Thompson was in the city for the UnitedHealthcare investors conference, which was set to begin at 8 a.m. Police noted that details of his schedule were widely available.

The shooter was not a guest at the hotel, though it remains unclear if he had other reasons to be there, authorities said.

After firing at Thompson from a distance, the gunman fled through the Ziegfeld alleyway and used a bike to make his escape.