UnitedHealthcare CEO killing latest: Luigi Mangione's lawyer has seen 'no evidence' linking gun to New York

ABC News' Peter Charalambous and Josh Margolin contributed to this report.

NEW YORK — Mangione, 26, plans to challenge his extradition from Pennsylvania to New York, where he faces a charge of second-degree murder in connection with Thompson's Dec. 4 outside a Midtown Manhattan hotel.