PORTLAND, Ore. -- Four armed robberies have been committed at neighborhood Portland bars in a little more than a week.

Now, people in the service industry are nervous their bar could be next. Portland police want to catch the two men, one armed with a gun and the other with a knife, who are doing it -- before things get more violent.

"Sometimes it's because of drug addiction, heroin or opiod addiction. Other times it's just about money, it's about the thrill of it, or excitement," said Portland Police Sgt. Pete Simpson.

Two men in hooded sweatshirts are on clear surveillance video robbing the Lotsa Luck Bar and Grill on Powell Boulevard back on June 2. Police are looking at whether the duo did similar robberies at the Blue Fin Bar on Northeast Sandy, the Lodge Bar on Southeast Powell and the Jolly Roger on Southeast 12th Avenue.

"They were shouting and the guy with the gun was waving it around and the guy with the knife had it threatening everyone with it, they were not gentle about it," said Kaitlyn Clark, who was working behind the bar counter during the robbery at Jolly Roger.

"It's terrifying, you're trapped behind the bar and you're sort of at the mercy of people coming in," said Jeffrey Morgenthaler, bar manager of downtown's Clyde Common and Pepe Le Moko. He's also the founder of the Oregon Bartenders' Guild. "I think bars are a target partially because they're open and because they don't often come with a lot of security systems."

And that's what Morgenthaler and police agree on. Newer digital surveillance cameras with good lighting and proper placement can mean a quick arrest. Also a locked safe where you put a majority of your cash through the night, and locking the door right at last call, even if customers are inside can help you manage what's going on in the bar. It might prevent future robberies from getting more violent.

"There are times when people committing armed robberies get more aggressive and escalate things as they move on," said Simpson.

"I always advise bartenders, if somebody wants to rob the place, let them have it. No amount of money in a register is worth your life," Morgenthaler said.

Luckily no one has been seriously hurt yet. Police say at various times, they have several active robbers in the city. Even if these robberies aren't connected, it's better for bars to be proactive and get those security measures.