By Tasha Tsiaperas

Dallas Police Chief David Brown's public image has never been better. He is at the height of his national popularity, even making a cameo in a newly released music video.

But the city's top cop remains as private as ever. He was nowhere to be seen Thursday as his decision to retire was revealed on Twitter.

The announcement was made Thursday while Brown was on a golf trip with his wife in Austin, surprising many city leaders and his own staff.

He will step down on Oct. 22, his 56th birthday. But he says he won't publicly talk about his decision until Sept. 8, leaving many wondering why he's going now and what his plans are.

"Serving the citizens of Dallas in this noble profession has been both a true honor and a humbling experience," Brown said in a written statement.

Brown has worked for the Dallas Police Department for 33 years and was appointed to his current position in May 2010, making him the longest-serving police chief since 1960.

He gained national attention for the cool, collected way he handled the aftermath of a lone gunman's ambush on police officers as a downtown protest was ending July 7. Four Dallas police officers and one Dallas Area Rapid Transit police officer were killed. Nine others were injured.

Brown was praised by elected officials, community leaders and his own employees for how he handled the crisis. While deftly handling a hungry media and doing his best to comfort and share what he felt he could about the details of the tragedy, he also took the public and elected officials to task for what he said were growing burdens on an overworked, underpaid and underappreciated Police Department.

Soon, a social media movement was calling for him to be the next U.S. president. And his cameos in a Black Eyed Peas music video was released Wednesday night.

"The whole world learned what a special man leads our Dallas police" after the downtown ambush, Mayor Mike Rawlings said Thursday at a news conference with retiring City Manager A.C. Gonzalez at Dallas City Hall.

"David Brown is a straightforward man. He is a man of integrity and courage."

Executive Assistant Chief David Pughes has been named interim police chief. City leaders will conduct a national search for Brown's permanent replacement, though that is not likely to begin until next year, after a new city manager is hired.

Rawlings joked that he wished Brown would wait to retire after the end of his mayoral tenure in June 2019. He and the city manager said Brown has been mulling the decision to retire for a year.

"It wasn't a total surprise," Rawlings said. But, "July 7 happened, and we kind of forgot about it."

Brown referred to the downtown ambush in his retirement statement, saying he remembers "the brave men and women of the Dallas Police Department for their sacrifices to keep Dallas safe."

"I know the people of Dallas will never forget the ultimate sacrifice they made on the streets of our city that awful night," he said.

Brown called his decision to retire "difficult."

His more than six years as police chief were difficult, too.

As Rawlings put it, that's a long time to be top cop.

"Six years as chief of police is like 30 years in dog time," he said.

Brown's retirement announcement comes months after all four police associations called for new leadership in the Police Department and in the midst of tough salary negotiations.

After a sharp uptick in violent crime in March, Brown shuffled hundreds of officers from investigative positions and desk jobs into patrol spots. Rank-and-file officers were frustrated with the shift changes, and the police associations said they no longer believed Brown was effective as chief.

Now, the associations are unhappy with the department's pay and proposed raises that won't be divvied up evenly to all personnel. The department's starting pay of $44,659 is among the lowest in the state.

Brown pushed for increasing starting pay and hiring more officers to offset higher-than-expected attrition rates. He proposed adding 549 officers by next October, including 200 new positions.

The Dallas Morning News looked at the department's recruitment rate in the past and found that growing the department by such numbers in one year would be difficult, if not impossible. Last week, the city manager announced that the hiring push would be spread out over three years instead of one year as Brown had initially wanted.

Rawlings said he doesn't believe the chief's decision to step down has anything to do with spreading out the hiring.

At the height of his public career, but caught between his officers and his bosses, Brown apparently decided the time was right to go.

Pughes and the next police chief will inherit lingering issues at the department.

Gonzalez is still meeting with police associations to negotiate a three-year salary contract. The City Council will vote this month on the budget.

Those issues will affect the city's search for a new chief, said Dallas Police Association president Ron Pinkston.

"Any chief the city of Dallas is looking to recruit will look heavily at the commitment the City Council and city manager makes for public safety," he said. "Are we going to be able to recruit the best chief possible under these situations?"

Pinkston, like many others, said he didn't expect the chief's announcement Thursday.

"There were a lot of rumors that were floating around out there, but we were surprised," he said.

Sgt. Sheldon Smith, chief of staff for the Black Police Association of Greater Dallas, said his association has had disagreements with the chief. But "we celebrate his retirement with him," he said.

"It's an abrupt retirement," Smith said.

During his first weeks as chief, Brown's mentally ill 27-year-old son, David Jr., killed a Lancaster police officer and a bystander and was then killed by officers. It was Father's Day.

Former City Manager Mary Suhm said she and Brown spoke often during those days, when outsiders believed his would be a short-lived tenure. Suhm said Thursday she never doubted he would withstand the ordeal.

"His faith and his belief system got him through it," she said. "He's a strong person, too. That helped. But it was a tough time. A really tough time."

Since then, Brown has helped bridge the gap between Dallas officers and the city's black community.

He has seen both sides of the divide. His brother was killed by drug dealers in Phoenix, and his former patrol partner was killed in the line of duty.

Brown has often pointed to a defining moment in his career: Dallas hasn't seen the sort of riots seen in other cities after police shootings, but one started brewing in 2012 near Dixon Circle in South Dallas after a Dallas police officer killed an unarmed man.

It was the latest in a heavy string of police-involved shootings. Angry residents poured into the streets. Police in riot gear were soon face to face with several hundred people. But area pastors, police officers and members of the New Black Panther Party all moved quickly to defuse the situation by encouraging patience.

The chief quickly released details of the incident and changed the department's foot chase policy after the shooting. The officer killed the man after they got into a fight following a chase.

Brown has also implemented mandatory yearly de-escalation training for all patrol officers, and his top commanders and police managers have undergone racial bias training.

After the downtown ambush, President Barack Obama praised the Police Department, saying it is an example to other agencies because it has "drastically reduced complaints about police misconduct."

Texas Gov. Greg Abbott issued a statement Thursday thanking Brown for his leadership during the Dallas ambush.

"At no time was his exemplary leadership more evident than in the aftermath of the heinous shooting of law enforcement officers this July in Dallas," read the statement. "Thanks to his unwavering commitment to protecting his community, Dallas has emerged even stronger, and on behalf of the entire state of Texas, Cecilia and I thank him for his service."

(Staff writers Robert Wilonsky and Naheed Rajwani contributed to this report.)

(c)2016 The Dallas Morning News