(CNN) After a nearly two-month search, Tampa police arrested a 24-year-old man on four counts of murder in connection with a series of fatal shootings that had terrified residents in the city's Seminole Heights neighborhood.

Howell Donaldson III was taken into custody Tuesday afternoon at a nearby McDonald's after police recovered a gun that they said had been used in the four killings.

Donaldson admitted that he owned the gun but did not admit to the killings, Tampa Police Chief Brian Dugan said, but police are convinced that they finally caught the person responsible.

"We've had other guns, but we knew this was the one," Dugan said. "Now the work begins to shore up the case and get a full prosecution."

Howell Emanuel Donaldson III has been arrested on four counts of murder, police said.

The arrest came 51 days after the first of four shootings in Seminole Heights, each of which targeted citizens doing ordinary things, like waiting at a bus stop or crossing the street. The four seemingly unconnected victims were each killed -- but not robbed -- while walking alone at night within a half-mile area, police said,leading to fears of a serial killer on the loose.

In the past month, officers swarmed the tree-lined neighborhood, advising residents not to go outside alone, to be alert and keep their porch lights on. Some residents stopped walking their dogs, running outside, going for walks or waiting for the bus alone, saying they no longer felt safe.

Police said they didn't yet know the motive for the killings or why the Seminole Heights neighborhood was chosen.

"He was friendly and nice to the cops, but he didn't give us anything. He didn't tell us why he was doing it, or anything like that," Dugan said.

For weeks, officials had said they were not calling the shooter a serial killer . But on Wednesday, Tampa Mayor Bob Buckhorn said he was proud of the city, which "has now spent the last 51 days dealing with a serial killer."

The arrest

From left to right: Anthony Naiboa, Monica Hoffa, Benjamin Mitchell and Ronald Felton were shot and killed in separate incidents in the Seminole Heights neighborhood.

Police said they received a tip on Tuesday around 2:40 p.m. f rom a McDonald's manager about a man who had a gun in a bag at the fast food restaurant. The McDonald's is about two to three miles from where the killings took place.

Donaldson worked at that McDonald's, Dugan said, and went there earlier in the day. He gave the manager a gun in a paper bag for safe-keeping, police said. The manager then gave the weapon to a police officer, who called for backup and detained Donaldson for more questioning.

A coworker told police that Donaldson had expressed his intention to leave the state, according to the criminal affidavit.

Donaldson purchased a Glock firearm on October 3 and picked it up on October 7 after the mandatory waiting period, the affidavit states. He also purchased Sig Sauer .40-caliber Smith & Wesson ammunition, on October 7, according to the police.

In an interview with police, he said that no one else had control of the firearm since he purchased it, according to the affidavit. He also said he was unfamiliar with Seminole Heights.

Fired SIG brand Smith & Wesson .40 caliber cartridges were found at three of the shooting scenes, according to the affidavit. An examination of Donaldson's Glock firearm and the cartridge casings recovered at the scenes showed that the casings had been fired from his weapon, the affidavit stated.

Location data on his cell phone corresponded to an address near the killings at times when three of the homicides occurred, according to the affidavit.

In addition, the report states that Donaldson consented to a search of his vehicle, where police found clothing similar to that worn by the suspect in surveillance footage. The clothing appeared to have the presence of a suspected blood stain, the affidavit stated.

Dugan told reporters late Tuesday night about the arrest of Donaldson, even though authorities hadn't finished drawing up the charges against him. He said they wanted to get out the news of the arrest quickly to reassure the Seminole Heights community.

"The real goal is to let the people of Seminole Heights be able to get a good night's sleep," Dugan said. "It's been 51 days that they've been terrorized in their neighborhood and it is about letting these families know that we're going to bring this person to justice, and letting this neighborhood get some rest."

Donaldson is scheduled to make his first court appearance on Thursday. He has not retained an attorney and will likely be appointed one at his court appearance.

Suspect was on university basketball team

Donaldson attended St. John's University in New York beginning in fall 2011 and graduated in January 2017, according to Brian Browne, executive director of University Relations.

He was a walk-on for the men's basketball team during the 2011-2012 season but never played in a game, Browne said.

His freshman-year suitemate at St. John's said Donaldson introduced himself as "Trai" in the fall of 2011. The suitemate, who asked to not be identified, said they lived in the same suite the entire year, until Donaldson got an off-campus apartment.

When college friends sent the former suitemate Donaldson's mugshot early Wednesday morning, "my mouth dropped," the former suitemate said, still in shock.

"It's just like, what? Not Trai. I just don't see what his motive would be."

His first impression of Donaldson was that he was quiet, although the suitemate admitted that was typical the first few days of school. He said Donaldson had the best manners, dressed very well, and was a sneakerhead.

He said he never saw him angry, and at parties, he said Donaldson was a wallflower.

"[Trai was] just a regular guy," the former suitemate said. "Nothing stood out as violent."

Officials said they still had several unanswered questions about the motive for the killings.

"We're still trying to figure out this person's ties to the neighborhood," Dugan said. "We're not sure why he was in this neighborhood or what his motive is. There's still a lot more to go in this investigation."

The victims

The victims seem to have been selected at random, leaving the community on edge as the number of unsolved shootings mounted.

Benjamin Mitchell, 22, a full-time student at Hillsborough Community College, was shot and killed at a bus stop in the Seminole Heights neighborhood October 9.

Monica Hoffa, 32, a waitress, was shot and killed October 11. Her body was found two days later in a vacant parking lot.

Anthony Naiboa, 20, who had autism and had just started a temporary job packing relief supplies for hurricane victims in Puerto Rico, was shot October 19 when he accidentally got on the wrong bus and ended up in Seminole Heights.

Ronald Felton, 60, who worked in construction and had three grown children, was shot in the back on November 14.

Relief in Tampa

Florida Gov. Rick Scott, who had visited Seminole Heights last week, said he had seen "firsthand the pain that these crimes have caused across the community."

It's been 51 days and it's time for Seminole Heights to have a good night's rest. pic.twitter.com/USQip4frCt — Bob Buckhorn (@BobBuckhorn) November 29, 2017

"In Florida, we have absolutely zero tolerance for this type of evil behavior and anyone responsible will be held to the fullest extent of the law," he said in a statement.

On Wednesday, Scott thanked Tampa police and other law enforcement agencies for working around the clock to solve the confounding case.

"Why somebody would have it in their mind to go take four individuals' lives, I just don't get it," Scott said. "And I don't know that we'll ever understand."

Buckhorn praised the "tired" law enforcement authorities who had worked 24 hours a day to solve this case.

"Today was a good day. Today, the good guys won. Today, Seminole Heights can sleep," he said.

"Today we begin the healing process. And today, the judicial process starts. And it will end. And I can promise you that when it does end, that this community will be a better place. Because I know where this guy is gonna spend his eternity."

Family member reaction to arrest

A makeshift memorial for shooting victim Anthony Naiboa sits on a sidewalk in the Seminole Heights neighborhood of Tampa on October 24.

Maria Rodriguez, the stepmother of Naiboa, told CNN she was happy no more people will be harmed.

"We're relieved to a point. Justice has been served so far," she said.

Rodriguez said her family plans to follow the legal proceedings in the case.

"I want to be there because I want this person to get the death penalty," she said.

In late October, Dugan released blurry video of a "person of interest" wearing a hooded jacket casually walking down a street near one of the killings.

The police chief released new video about two weeks ago showing a similar-looking person with the same gait who was present near the last shooting, that of Felton. The person in the video, Dugan said then, had become a suspect.

Based on a witness statement, Dugan initially described the suspect as a black male between 6 feet and 6 feet 2 inches with a thin build and a light complexion. The surveillance images were in black and white.

The suspect was wearing all black and a black baseball cap and armed with a large black pistol, police said.

CORRECTION: An earlier version of this story misstated that Howell Donaldson III was charged with four counts of murder, according to verbal and written statements from Tampa police. The state's attorney later clarified that he was arrested on four counts of premeditated murder and that a grand jury must indict him before he could be charged.