PHOENIX >> Since the summer of 2015, metropolitan Phoenix has been roiled by two serial shooting cases in which an attacker has fired gunshots at targets from a vehicle.

In one case, a gunman instilled fear among motorists by firing on several vehicles on the metro area’s freeways. In the other, police say a man dubbed the Serial Street Shooter killed nine people in nighttime attacks launched from his car, all but one of them targeting random victims.

Police say there’s no evidence connecting both series of shootings, despite their similarities.

Here’s an explanation about the two investigations.

FREEWAY SHOOTINGS

Drivers were on edge for several weeks in August and September of 2015 as 11 vehicles were shot on Phoenix-area highways. The shootings sowed so much fear that people avoided driving the freeways, school buses took different routes, and signs were posted telling people to be careful.

Eight cars were hit with bullets and three others were struck with projectiles such as BBs or pellets. The only injury occurred when the ear of a 13-year-old girl was cut by glass.

In the weeks after the shootings, Leslie Merritt Jr., then a 21-year-old landscaper, was charged in four of the 11 shootings. Authorities say Merritt was tied to the shootings through ballistics tests.

But the charges were dropped after an expert said that the Arizona Department of Public Safety’s crime lab had incorrectly concluded that ballistic evidence linked Merritt’s 9-mm handgun to the shootings.

Merritt, who vigorously insisted that he was innocent, was freed last year after spending seven months in jail. No one else has been arrested in the freeway shootings, and authorities say the investigation into the attacks continues.

The head of the Department of Public Safety told The Associated Press last week that his agency still “unequivocally” believes Merritt’s gun was the one used in the freeway shootings, even though prosecutors dropped Merritt’s charges.

“We believe that it was the right gun, and I believe the work that the crime lab did on that particular gun is accurate,” Frank Milstead said.

Merritt has brought a lawsuit against the state claiming that authorities falsely accused him when they knew their evidence was weak. His lawyers have said Merritt is seeking $10 million.

SERIAL STREET SHOOTER ATTACKS

Around the same time of the freeway shootings, Phoenix police say a gunman killed a man outside his home in central Phoenix and went on to take the lives of eight more people in 2016. They called him the Serial Street Shooter.

Police say the victims were attacked as they stood outside their homes or sat in vehicles after dark. They were fired upon by a man who was sitting in a car or had just stepped out of his vehicle.

Police this week booked 23-year-old Aaron Saucedo on suspicion of carrying out the attacks. They say his victims include a 21-year-old man whose girlfriend was pregnant with their son and a 12-year-girl who was shot to death along with her mother and a friend of the woman. No motive has been established.

The shootings unnerved residents of a largely Latino neighborhood, leading some people to remain inside after dark.

The attacks stumped investigators for several months last year, despite eyewitness accounts that correctly identified the type of car Saucedo drove — a BMW sedan — and provided a police sketch with a striking resemblance to the suspect.

Saucedo insists he’s innocent. Investigators declined to detail the evidence they say implicates Saucedo in the attacks.

TESTING THE GUNS

In a strange coincidence, the case into the freeway shootings prompted investigators to seize the weapon police say Saucedo used to carry out his first killing.

Evidence from the freeway shootings showed that the culprit was using a Hi-Point 9-mm handgun. Department of Public Safety investigators began seizing that type of gun from pawn shops around Phoenix in the hope of finding a match to the freeway case.

As it turns out, police say Saucedo also used a Hi-Point 9-mm pistol in his first killing and sold the gun two weeks later to the same pawn shop where Merritt also pawned his weapon.

Investigators test-fired Saucedo’s gun, but they never conducted ballistics tests on it and returned it to the pawn shop five days later once they ruled it out the freeway shootings. Saucedo remained on the streets before launching his random attacks four months later.

Phoenix police have refused to comment about what efforts, if any, they undertook to investigate Saucedo in the immediate aftermath of the first killing. Phoenix police say he left behind bullet fragments, shell casings and knew the victim, but they didn’t examine his weapon until 20 months later.

YET ANOTHER SERIAL SHOOTING CASE

This isn’t the first time Phoenix has faced a series of random shootings.

More than 10 years ago, six people were killed and 19 others were wounded in random nighttime shootings.

The case was solved after a drinking buddy of one of the two killers told police that his friend had bragged about shooting people.

The drinking buddy’s tip led to the conviction of two men.