(Photo by St. Louis County Prosecutor's Office via Getty Images)

FERGUSON, Missouri (AP) — The white police officer who killed an unarmed black 18-year-old resigned from his job with the Ferguson Police Department after learning of threats of violence against other officers and the department, his lawyer said Sunday.

Darren Wilson, 28, had been on administrative leave since Aug. 9, when he shot and killed Michael Brown. A grand jury decided Monday not to indict Wilson, sparking days of sometimes violent protests in Ferguson and other cities across the U.S.

Wilson wrote in his resignation letter that his “continued employment may put the residents and police officers of the City of Ferguson at risk, which is a circumstance I cannot allow.”

His lawyer, Neil Bruntrager, told The Associated Press that Wilson decided to step aside after police Chief Tom Jackson told him about the alleged threats on Saturday.

“The information we had was that there would be actions targeting the Ferguson (police) department or buildings in Ferguson related to the police department,” Bruntrager said. He said Wilson, who had worked for the department for less than three years, and the city were already discussing an exit strategy, acknowledging that staying on as an officer there would be impossible.

Ferguson’s mayor said Sunday that Wilson did not receive any severance package. Wilson won’t receive any further pay or benefits, and he and the city have severed their ties, Mayor James Knowles told reporters a day after Wilson tendered his resignation, effective immediately.

Many have criticized the authorities’ handling of the case, but Knowles said no leadership changes were in the works. Asked if he would resign, Jackson said flatly, “No.”

Benjamin Crump, an attorney for Brown’s family, said Wilson’s resignation was not a surprise.

“It was always believed that the police officer would do what was in his best interest, both personally and professionally,” Crump said. “We didn’t believe that he would be able to be effective for the Ferguson community nor the Ferguson Police Department because of the tragic circumstances that claimed the life of Michael Brown Jr.”

Crump said the family is still considering civil litigation such as a wrongful death lawsuit, “but don’t let that get confused with the fact that they really wanted the killer of their child to be held accountable.”

On Saturday night, more than 100 protesters gathered near Ferguson police headquarters, where they were outnumbered by officers. Two people were arrested. Another protester burned an American flag. By midnight, only about two dozen protesters remained. Many seemed unfazed by Wilson’s resignation. Several merely shrugged their shoulders when asked what they thought.

Wilson has spent his entire adult life as a police officer, first in neighboring Jennings, then in Ferguson. Bruntrager said it’s all he’s ever wanted to do.

“In terms of what it (the resignation) means, it means at this point he doesn’t have a paycheck,” Bruntrager said. “He has no income so he’ll have to make some decisions pretty quickly.”

Wilson fatally shot Brown in the middle of a Ferguson street after the two scuffled inside Wilson’s police SUV. Brown’s body was left for more than four hours as police investigated and angry onlookers gathered.

In the days after the shooting, tense and sometimes violent protests occurred in and around Ferguson, a predominantly black community patrolled by a mostly white police force. Missouri Gov. Jay Nixon called in the National Guard to help.

Some witnesses have said Brown had his hands up when Wilson shot him. Wilson told the grand jury that he feared for his life when Brown hit him and reached for his gun.

The U.S. Justice Department is conducting a civil rights investigation into the shooting and a separate investigation of Ferguson police department practices. It isn’t clear when that decision will be announced.

There were 12 commercial buildings in Ferguson that were destroyed by fire after the grand jury’s decision was announced, and there have been well over 100 arrests at St. Louis-area protests in that time.

Knowles said there hasn’t been a cost assessment of the damage in Ferguson yet, and he promised residents and businesses that the city will do all it can to seek financial help.

“We are committed to rebuilding our city,” he said.

Reverberations of the Ferguson events were evident at the St. Louis Rams’ pro football game.

Inside the Edward Jones Dome, five Rams players engaged in their own apparent show of solidarity for Ferguson protesters, standing with their arms raised in a “Hands Up” gesture before trotting onto the field for pregame introductions. All five — Tavon Austin, Kenny Britt, Stedman Bailey, Jared Cook and Chris Givens — are black.

After the game, about 100 protesters marched in the area near the Edward Jones Dome, chanting, “Ram fans — join the movement.” When about three dozen St. Louis officers in riot gear showed up to make sure things didn’t get out of hand, many of the fans broke out in spontaneous applause for the officers.

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