Arlington County Police Chief Edward A. Flynn, who stepped onto the national stage while directing the department's response to the Sept. 11, 2001, terrorist attack on the Pentagon, is leaving for a cabinet-level public safety job in the administration of Massachusetts Gov.-elect Mitt Romney, officials said yesterday.

Flynn, a 30-year police veteran, was tapped to become secretary of the Executive Office of Public Safety, a post with broad planning and administrative duties. The department, headquartered in Boston, oversees 21 agencies, including state police, corrections, and emergency management and has new homeland security duties.

Instead of a 460-member force with an annual budget of $36 million, he will have responsibility for a budget of about $1 billion and 10,000 employees. For accepting greater responsibility, however, Flynn will receive slightly less: $118,000 a year, compared with $121,000 in his current job.

"When they call it public service, they're not kidding around," Flynn said yesterday by telephone from his hotel in Massachusetts.

He said he felt "bittersweet" about leaving. "I loved this Arlington job. It's the best police job you could have."

But Flynn said he also was excited to take on a larger challenge.

"I had never had a governor-elect call me up before saying, 'We need you here,' " Flynn said. "I didn't know how to say no."

Arlington County Manager Ron Carlee and County Board members lavished praise on Flynn as a smart, articulate and effective police chief who left his mark through community policing.

To decentralize, for example, Flynn divided the small county into four districts in 1998 and gave each district commander greater responsibility. He also recruited and promoted minorities and built bridges with neighboring law enforcement agencies, officials said.

"I certainly congratulate the governor of Massachusetts for getting one of the most highly respected law enforcement officers in the country," Carlee said. He said he particularly admired Flynn's pronouncement after the terrorist attacks that the county would not tolerate hate crimes against Muslims.

"In a very eloquent way, he said, 'Don't try it here.' "

Under Flynn, 11 percent of the 330 sworn officers and 19 percent of the ranking officers are African American -- compared with 9 percent of the county's population. In June, Flynn made Rebecca Hackney deputy chief -- the first woman appointed to that job permanently.

Yet Flynn has detractors who found his style brusque and aloof. "He also balkanized the police department. Simply by splitting up the police department, they spent more time fighting each other than fighting crime," said John Antonelli, a frequent critic of county government.

Flynn, whose wife of 29 years is a guidance counselor at Williamsburg Middle School, was appointed in September 1997 to succeed William K. "Smokey" Stover. Stover retired after 40 years on the force.

Flynn was selected from a pool of 150 candidates after an eight-month search. He had been a police officer for more than 25 years. He served nine years as chief in Chelsea, Mass. He also was the chief in Braintree, Mass., from 1988 to 1993. He began his police career in 1971 as a patrol officer in Hillside Township, N.J.

Serious crimes dropped about 16 percent from 8,306 in 1997, when Flynn took over, to 6,956 in 2001.

"He was a great police chief," board member Barbara A. Favola (D) said. "He embodied the values that I want the police to embrace every day."