Arizona and federal authorities announced on Saturday that evidence from shell casings and bullet fragments determined that a firearm the suspect pawned was used in four of the 11 Interstate 10 freeway shootings.

The Arizona Republic reports that two law enforcement officials attributed the arrest of Leslie Allen Merritt Jr., 21, to a combination of ballistics, “shoe-leather police work” and Merritt’s social media presence.

Merritt is facing a total of 28 felony charges, including four counts each of intentional terrorism, committing a drive-by shooting, endangerment, aggravated assault with a deadly weapon, criminal damage, disorderly conduct and discharging a firearm within city limits, the Republic reports, citing court documents.

Tom Mangan, a special agent with the Bureau of Alcohol, Tobacco, Firearms and Explosives, which has been assisting in the case, said the evidence gathered by the Department of Public Safety leaves “no doubt” the gun used was the one owned and pawned by Merritt.

The bullet recovered contains certain hand and groove impressions after it’s been fired that are unique to a particular firearm, Mangan said.

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The charging document released Saturday night said that investigators determined by testing that the bullets and the bullet fragments from four incidents came from a gun that was owned by Merritt. The test of Merritt's gun by the Arizona Department of Public Safety "fired bullets (that) were matched to the bullets and bullet fragments from the four cases ...," the document said.

A man who identified himself to the Associated Press as a manager at Mo-Money Pawn declined to comment Saturday beyond a post on a Facebook page that said detectives contacted the shop Wednesday looking for a certain caliber and make of a handgun and examined several weapons.

Department of Public Safety Director Frank Milstead said the investigation continues into who is behind the other shootings.

Merritt was arrested late Friday night outside a Glendale Wal-Mart after Swat team swarmed the store. Minutes later, Gov. Doug Ducey tweeted, “We got him!”

Superior Court Commissioner Lisa Roberts set bail at $1 million, and Merritt asked, in a soft-spoken voice, to address the court.

"All I have to say is I'm the wrong guy. I tried telling the detectives that. My gun's been in the pawn shop the last two months. I haven't even had access to a weapon," he said as he stood handcuffed in a black and white striped jail uniform.

Merritt told the judge he would have a hard time raising the bail amount.

“I could never afford that bond,” he said. “I got two kids.”

Merritt also told detectives that he was not in possession of the gun because it was pawned, but investigators say that wasn’t the case during the shootings. The Republic reports he also told detectives he had been in possession of a gun since he bought it new and up until the point when he pawned it, according to court records.

Eleven total vehicles were hit by bullets or other projectiles, such as BBs or pellets, while driving along Phoenix freeways between Aug. 29 and Sept. 10. There haven’t been any serious injuries, although a 13-year-old girl’s ear was cut when a bullet shattered a car window she was sitting in.

Messages seeking tips about the shootings will remain posted on electronic signs along freeways, and a $50,000 reward is still available, Graves said.

In an interview with The Associated Press, Merritt's father was adamant that his son had nothing to do with the shootings and anyone who says he was involved is a "moron."

Leslie Merritt Sr. said he believes his son is being made a scapegoat by police who were desperate to make an arrest under immense public pressure.

"He has way too much value for human life to even take the slightest or remotest risk of actually injuring someone," the elder Merritt said. He said his son likes guns but is not a criminal.

Merritt Jr.'s Facebook page, confirmed by his father, has two video clips that show him firing guns into the desert toward a palm tree, exclaiming "whoo" after squeezing off a round.

The Wal-Mart where Merritt Jr. was arrested Friday is 6 miles north of where some of the shootings occurred along I-10, a major route through the city.

The shootings prompted several school districts to keep their buses off freeways, and some commuters altered their routes.

Click for more from the Arizona Republic.

The Associated Press contributed to this report.