It started outside St. Louis in mid-September, when a man waiting at a bus stop was shot and severely injured by a stranger. The next day, the body of a teenage girl shot in the back of the head was found in the same neighborhood.
The unsolved shootings continued through the fall in impoverished Black neighborhoods across St. Louis and in Kansas City, Kan., 250 miles west. The authorities had no suspect and few clues, but the Missouri shootings had one critical thing in common: .40-caliber Smith & Wesson cartridge casings from the same handgun had been found at each location.
On Monday, law enforcement authorities in Missouri announced that they had arrested and charged a 25-year-old man suspected of killing six people and injuring two others in what appeared to be a series of random attacks.
The man, Perez D. Reed, who turns 26 on Wednesday, was charged with four counts of first-degree murder after the police tracked his cellphone and arrested him carrying a weapon that had been linked to all six shootings in Missouri.
The shooting of the man who was severely wounded at the bus stop on Sept. 12 and the teenage girl the next day were only the beginning, said Wesley Bell, the St. Louis County Prosecuting Attorney. Most of the attacks took place in predominantly Black areas of St. Louis marked by vacant lots and boarded homes.
Three days later, a woman was found with a fatal gunshot wound to the face at a gas station in St. Louis. The police followed a blood trail from the gas station, but the killer was not located.
About an hour later, the body of another woman, identified as Pamela Abercrombie, 49, was found about half a mile from where the blood trail had ended.
Another three days passed before the body of a 24-year-old man was found in a vacant lot not far away from the other killings — shot with a similar weapon.
“These are a lot of violent acts that occurred in a very brief period of time,” said Lt. Craig Longworth, of the St. Louis County Police Department. “These seem to be random acts. Why? I can’t give an answer to that.”
By Sept. 21, the police announced that the same gun had been used in three of the recent killings, and they raised a public alarm. Days later, there was another death: The body of a man was found in Ferguson, Mo., with gunshot wounds to the head and hand.
“The commonality amongst them were handgun casings. We knew they came from the same handgun,” Richard Quinn, the F.B.I. special agent in charge in St. Louis, told reporters on Monday. “We also had a description from several witnesses and one victim that had highlighted unique physical characteristics of the subject. However, that’s where we ran up against a little bit of a wall.”
Detectives got an important lead from the police in Kansas City, where two more murders occurred a few days apart in late October and early November in the same high-rise apartment building. According to the affidavit, Mr. Reed knew at least one of his victims there well enough to have exchanged hundreds of messages.
The police there had surveillance footage of a man with a crescent tattoo on his forehead leaving the scene. Mr. Reed, who has a crescent tattoo on his forehead, had left his ID at the front desk of the building, according to the affidavit.
On Friday, the police said, they learned that Mr. Reed had purchased an Amtrak ticket to return to St. Louis from Kansas City. They followed him. He got off a few stops short of his destination, in Independence, Mo., and when the authorities detained him, he had in his possession a handgun that they believed was linked to all the Missouri crime scenes.
Mr. Reed was initially arrested on a federal charge of transporting firearms across state lines with the intent to commit a felony. The city of St. Louis later charged him with two murders, and the county charged him with two more.
Although information about the Kansas killings is detailed in the court affidavit, no charges have been filed in those killings. No shell casings were found at those scenes, and investigators were awaiting results of DNA tests.
The Kansas City Police Department identified Mr. Reed as a “person of interest” in the two killings.
In questioning, Mr. Reed denied hurting anyone, and said he had found the gun that was in his possession, according to the affidavit.
Attempts to reach Mr. Reed’s lawyer and family members in St. Louis were unsuccessful.
In 2016, Mr. Reed was arrested and charged with setting fire to his family’s house. Prosecutors dropped the arson charges after family members declined to testify against him, St. Louis County prosecutors said.
In 2017, Mr. Reed sued the public defender’s office, accusing his own lawyers of “harassment” because he was being directed to submit to several mental health evaluations.
“I informed my attorney that I am mentally fine and repeatedly refuse to participate in the exam,” he wrote.
He said he had been traumatized by being exposed to violent “people and environment” in jail.
“My family has left me. I lost my job. I can’t pay child support, which is steady accumulating,” he wrote. The case was dismissed.
Court records also show he is in the middle of a divorce.
Officials said that Friday’s arrest was the result of cooperation between law enforcement agencies from several jurisdictions.
“This investigation and this arrest should hopefully provide some assurance to the community that law enforcement, across the board, despite the many, many obstacles put in their path over the past couple of years, is working very, very hard to protect, serve and hopefully provide justice for victims of these violent crimes,” said Sayler A. Fleming, the U.S. attorney for the Eastern District of Missouri.
Major Ryan Cousins, of the St. Louis Metropolitan Police Department, said he hopes the arrest offers solace.
“I hope this arrest somehow brings closure, at least a little bit, to their families,” he said.
Reporting was contributed by Eric Berger in St. Louis.