Riders have reported 42 bicycle thefts downtown as of this month, marking a 75 percent increase compared to the same time period last year, 6News' Jack Rinehart reported.

"We actually had a complaint last week from a man … he's had two bikes stolen from him at his relatives and one stolen from him. So in the past month, he's had three stolen,” said Lt. Steve Atzhorn.

Guillermo Bolanco said he watched his bike get stolen while he was working on a ladder on a downtown building.

"The guy was so fast and he took my bike,” he said. "I say you buy a chain and lock it good and don't trust nobody."

Just last week, police learned that lesson the hard way when someone stole a department training bicycle parked in front of Indianapolis Fire Department headquarters.

Officers are now leaving a high-end bait bike unattended in areas experiencing a high number of thefts.

On Tuesday, they arrested a 17-year-old minutes after the bike was left in front of the downtown library.

"We set it out in areas that are experiencing the larcenies of bikes to see if anyone takes it," said Lt. Steven Atzhorn. "We've done that for the past two days and have arrested a couple of people for taking the bike that actually belongs to the police department.”

Investigators said it’s that critical bike owners buy a substantial lock and use it every time they leave their ride unattended. They should also make a note of the serial number, found on the bottom of the frame, to report to police if it is stolen.

"I've never had a bike stolen. I always lock them up,” said downtown cyclist Jaxon West. “If you don't want your stuff to run away, lock it up."