Prosecutors have formally charged Leslie Allen Merritt, 21, for four of the 11 I-10 shootings that left residents in Phoenix terrified for weeks.

Merritt was charged with 16 felony counts: four counts of drive-by shooting, five counts of aggravated assault, three counts of unlawful discharge of a firearm, three counts of disorderly conduct and one count of endangerment, according to YourWestValley.

"I understand the frustration by some with respect to the limited amount of information released by the Department of Public Safety to date," said Maricopa County Attorney Bill Montgomery, according to ABC Arizona affiliate ABC 15.  "However, I am equally grateful for the caution necessary to safeguard any prosecution of the Defendant and the need to protect Due Process rights."

Despite authorities' insistence that the incident be considered an act of "domestic terrorism," prosecutors declined to file such charges, noting that Arizona's terrorism laws enacted after 9/11 don't apply to the freeway shootings.

Using the results from various ballistics tests, authorities were able to link Merritt to four of the 11 shootings. However, since state police believe that copycats might be shooting guns or other weapons onto the freeway, the investigation remains open, according to the Associated Press.

Ever since he was arrested Sept. 18 at a suburban Phoenix Wal-Mart, Merritt has maintained his innocence, claiming that the gun had been in a pawn shop at when the shootings began.

Merritt is in jail and is awaiting a court hearing scheduled for Friday.