Updated

After a series of mass shootings involving high-powered rifles across the country, police officers in Nashville's Metro Police Department are the latest to upgrade their firepower. Feeling outgunned, Metro Police Chief Steve Anderson announced a change in policy allowing officers to carry their own personal semi-automatic rifles -- after law enforcement in Newtown, Conn., and Aurora, Colo., faced gunmen who were armed with AR-15-style weapons.

"It has become increasingly clear that a pistol and a shotgun may not be enough for an officer to stop a threat to innocent citizens," Anderson said in a written statement. "This policy change is in the best interest of public and officer safety."

Anderson decided to allow officers to carry their own personal rifles after it was determined to be too costly for the department to purchase them for each of their 1,400 officers. The guns cost $800 to $1,200 each, depending on accessories.

The department estimates that one-third of the officers in the Metro Nashville police force personally own a rifle. Starting this year, they can carry them in their patrol cars after passing department inspections and training.

Other large agencies such as the Missouri Highway Patrol and Illinois State Police have also recently allowed officers to carry high-powered rifles in response to high-profile mass shootings and well-armed criminals.

But one small, suburban police force just outside Nashville was well ahead of that trend more than a decade ago - after a chaotic stand-off with an armed criminal.

Police officers in Brentwood, Tenn., had no idea what they were up against when they responded to a robbery call at the Bank of America on May 6, 2002. But a dashboard camera recorded the chaos as bullets peppered arriving patrol cars, windshields shattered and officers tried to take cover.

"I have worked out here for 24 years now and it's a nice community," said Brentwood Assistant Chief Tommy Walsh - one of the first officers responding to the scene.  "I never thought that a suspect would be standing in the middle of the street firing an assault weapon at me."

The suspect was still in the area, on foot and armed with an AR-15 rifle. The officers faced multiple rounds being fired at them and their cars. Walsh was one of two officers hit in the hail of bullets.

"I fired a shot at the suspect as he was reeling towards me with the rifle," Walsh said. "The shot I fired missed, unfortunately. And the first shot the suspect fired at me went through the door of the patrol car and struck me in the leg."

The suspect was eventually killed, and both officers recovered from their injuries. The Brentwood Police Department was left with a stark reality that officers armed with handguns would be no match against criminals brandishing rifles that could fire multiple rounds per second.

Struggling with tight budgets, former Brentwood Police Chief Ricky Watson went to local businesses and residents who helped him raise more than $50,000 to buy the rifles.

"Historically, the weapon of choice for most police departments has been a Remington 870 shotgun. And we had those for all our officers," Watson said. "But in an urban setting at a distance, the shotgun is not as effective as a rifle would be. So I made a determination at that point in time to figure out a way to upgrade our weapons to include a patrol rifle."

Though Brentwood officers haven't had to use the rifles in service during the 11 years following the bank robbery, current Police Chief Jeff Hughes says it's peace of mind just to have them every time his officers hit the streets.

"Just because we are an affluent community here in Tennessee, we are not immune to anything in a bigger city, or some of these other cities that have experienced active shooter scenarios," Hughes said. "We are not immune to it any more than they were."

Each agency has strict guidelines on when use of the rifles is warranted and how they should be stored. Under Nashville's new policy, patrol rifles are not intended for routine calls and are to be used only "when it's clear that a tactical advantage over a criminal suspect is warranted."