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Oct. 1, 2015, 4:29 PM GMT / Updated Oct. 1, 2015, 4:30 PM GMT By Erik Ortiz

The gunman suspected of terrorizing Phoenix-area drivers in a series of highway shootings pleaded not guilty Thursday to the felony charges against him.

Leslie Allen Merritt Jr., 21, was arraigned in Maricopa County Superior Court on 15 counts — including for drive-by shooting, intentional acts of terrorism and disorderly conduct involving a weapon.

Prosecutors say Merritt, a landscaper, was involved in the first four of 11 shootings that targeted random drivers on Interstate 10 over two weeks. The first three shootings took place Aug. 29, and the fourth occurred the following day, police said.

The charges associated with each shooting carry more than 100 years in prison,NBC affiliate KPNX reported.

While vehicles were damaged by bullets, no one was seriously hurt. A 13-year-old girl was injured by flying glass, but she refused treatment.