“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.