PHOENIX — Soft-spoken and handcuffed, a 21-year-old landscaper insists that he is not responsible for a string of Phoenix freeway shootings and that his gun has been sitting in a pawn shop for months.

Despite Leslie Allen Merritt Jr.’s impromptu assertion in court Saturday, investigators said they have proof that the gun wasn’t in any pawn shop at the time of four shootings they say he carried out.

Newly released charging documents detail the detective work that traced the gun to the suspect after he took it to a pawn shop. Weapons from various local pawn shops were test-fired at the state lab, Arizona Department of Public Safety spokesman Bart Graves said.

The Glendale resident faces several charges, including aggravated assault, criminal damage, disorderly conduct, carrying out a drive-by shooting and intentional acts of terrorism. Merritt told a judge that authorities have “the wrong guy.”