Story highlights

NEW: The slain officer's family remembers him as a caring, devoted man who "lived a life defined by duty"

Police chief: Before the shooting, the suspect had "clearly demonstrated" he was violent

Authorities say suspect Tremaine Wilbourn has surrendered

CNN  — 

The man accused of killing an officer in Memphis, Tennessee, has surrendered to authorities, but the case is far from over, the city’s police chief said.

“This is just the first step in a very long healing process,” Memphis Police Director Toney Armstrong told reporters Monday.

Tremaine Wilbourn, 29, turned himself in to federal marshals and was being questioned by homicide investigators Monday evening, Armstrong said. He’s expected to be arraigned on Wednesday.

Investigators, who’d warned that Wilbourn was armed and dangerous, had been working round the clock to track him down, the police chief said.

“I think he felt the walls closing in,” Armstrong said. “I think he thought that it would probably be in his best interest just to turn himself in.”

But even with the suspect behind bars, the police chief noted there’s a key question that remains in the case: Why was he on the streets in the first place?

“If he’s in jail Saturday night, then we’re not here today talking about the death of a police officer,” he said.

Wilbourn had been out on supervised release for a 121-month sentence for robbery.

“All the signs were there,” Armstrong said. “His actions had clearly demonstrated that he was a violent individual, and I have a thing that I tell people all the time, anybody that robs somebody is one step away from killing somebody.”

Police chief: Slain officer interrupted drug deal

It started as a regular traffic stop on a weekend night in Tennessee. Officer Sean Bolton saw an illegally parked car on the streets of Memphis, pulled up in front of it and shone his spotlight.

When he approached the vehicle, a passenger confronted him.

A struggle ensued, and the passenger shot Bolton multiple times, authorities said. The car drove off, leaving the officer for dead.

Memphis Police officer Sean Bolton was shot and killed during a traffic stop.

“Officer Bolton apparently interrupted some sort of drug transaction,” Armstrong said. “A digital scale and a small baggie of marijuana … were located inside of the vehicle.”

The violence was senseless given how mundane the stop was, Armstrong said.

“We’re talking about less than 2 grams of marijuana. You’re talking about a misdemeanor citation,” he said. “We probably would not have even transported for that.”

Memphis police officer killed; suspect identified

Bolton loved to read, work out

Nearby residents heard the gunshots late Saturday night and used Bolton’s radio to call for help. Emergency crews took him to a hospital in critical condition, where he was later pronounced dead.

Armstrong described the suspect as a “coward.”

“You gunned down, you murdered a police officer, for less than 2 grams of marijuana,” he said. “You literally destroyed a family.”

Friends described the Iraq veteran as a gentle man who did not believe in using force.

“For a police officer to have that kind of temperament, and to take such a cautious approach to the use of force, he was a credit to the uniform,” his friend Steve Clements told The Commercial Appeal newspaper in Memphis.

Bolton was quiet and loved to read and go to the gym, friend Minda Klitzner told the paper.

So much so, he’d read in the car during road trips.

Fallen officers

Bolton, 33, is one of 19 officers killed nationwide this year by violent suspects. The deaths at the hands of suspects run the gamut – veterans and rookie officers – and span the nation from Georgia to California

“Last night, we lost not only an officer, but a great man, a dedicated servant to our community and a family member,” Armstrong said.

This is the third time a Memphis police officer has been killed in the past four years.

Bolton’s family remembered him as a humble, devoted and caring man who spoke several languages, read voraciously, practiced martial arts, ran 5K races, played numerous sports and helped the people of Memphis in myriad ways – having returned there after his time in the Marines.

“Sean Bolton lived a life defined by duty,” the family said in a statement, released through the Memphis Police Department.

“… While he had offers to leave the police force and do other types of law enforcement, he loved being on the streets of his hometown. Sean genuinely wanted to help all Memphians to live safely and peaceably within our community.”

CNN’s Greg Botelho, Kevin Conlon and Rashard Rose contributed to this report.