Police stormed a bathroom with guns drawn to catch a burglar. They found a Roomba.

Pounding noises kept coming from the bathroom in a suburban home outside Portland, Oregon. Cops had surrounded the door, and a trained canine panted nearby. The officers unholstered their guns, shouted that they were police and demanded that the burglary suspect holed up inside let them in.

No response. Just more banging. Probably, the police decided, the intruder was trying to force open a window to run away.

All at once, the cops burst in, ready to fire.

Then, they saw it: a little Roomba robot vacuum, stuck in a corner and slamming repeatedly into the shower door.

The deputies convulsed. And one of America's first brushes with robot-versus-law enforcement conflict, thankfully, ended without violence.

"There was just immediate laughter," Sgt. Danny DiPietro, a spokesman for the Washington County Sheriff's Office, said in an interview with The Washington Post. "They didn't know what was going to happen. They're ready for anything and then it was like, 'Whoa, what? What's going on here? Am I being pranked?'"

In fact, the call for assistance was no joke. Two men dialed 911 at 1:48 p.m. on Monday, the sheriff's office said on Facebook, to report that someone had broken into a home in the Cedar Hills neighborhood just outside Beaverton, Oregon, about seven miles west of downtown Portland. The intruder was locked in the bathroom, the caller said, adding that he could see shadows moving under the door.

A detective happened to be nearby and rushed to the scene. Within minutes, he was met by three other deputies from the sheriff's office and two canine officers from Beaverton's police force, DiPietro said. They soon learned the full story from the worried callers.

"There were two gentlemen house sitting for their nephew, who is an adult. They go out to walk the dog and when they come back, they hear something in the bathroom," DiPietro said. "The door is shut and locked, and they believe someone is in there. So they called the police, like anyone would."

The officers on the scene didn't take any chances. They loudly announced their presence, warning the intruder that they'd been caught in the act, and then sent in one of the trained police dogs. Whoever was inside wouldn't surrender.

When the cops came into the house, they could hear "rustling" in the bathroom, Deputy Brian Rogers wrote in a note recounting the incident.

That's when they surrounded the bathroom, ready for the worst. Whoever was inside wasn't just ignoring police orders, they were making a commotion as they presumably plotted an escape.

"One hundred percent, they had their guns out and the dogs out," DiPietro said. "If we tell you we're the police and you're not responding and not coming out, we don't know what we're walking into. We don't know if they're armed or if they're going to attack us."

Only after rushing the room and then collapsing into a fit of laughter did the deputies work out what had happened.

"We breached the bathroom door and encountered a very thorough vacuuming job being done by a Roomba Robotic Vacuum cleaner," Rogers wrote.

The two men, who were hugely apologetic, had no idea their nephew owned a Roomba. After the department gleefully recounted the saga on its Facebook page under a faux "Most Wanted" poster featuring a Roomba, hundreds of commenters jumped in to laugh at the callers' plight.

But DiPietro defended the would-be robot vacuum burglary victims.

"They were definitely embarrassed, but our deputies told them, 'Hey, we believed it was an intruder, too,'" DiPietro said. "These people were house sitting. They didn't know this vacuum was going to kick on and go and do this ... These people were in a unique circumstance."

The foiled robot robbery will long be retold around the Washington County Sheriff's Office, DiPietro said.

"Every call is unique, and this was a fun one," he said. "There are a lot of parts of our job that can be not the best. This is one that is going to stick in your mind for a long time for a good reason."