A grandfather has been praised for deftly tripping an armed suspect who was running from the police, allowing officers to make an arrest.

The man, identified only as "Bill" by police, had just left a library in Columbus, Ohio when he saw the suspect running in his direction.

Police said Bill heard officers yelling multiple times to drop the gun.

"Bill assessed the situation as fast as he could, cane in hand," Columbus Police said in a Facebook post.

"I could see that he was holding something in his waistband while he was running," Bill said.

"He was coming my way, so I got in his way to slow him down so you guys could get him."

Bill said he noticed the suspect "holding something in his waistband". ( Supplied: Columbus Police Department )

Bill then stuck out his back leg to trip the fleeing teenage suspect. The suspect's gun flew out of his hand and police quickly piled on him.

Police identified the suspect's weapon as a "Glock 9 MM pistol with a high capacity extended clip containing 29 rounds".

The grandfather's move, which was captured by surveillance cameras, "likely saved the 18-year-old suspect's life," according to the police statement.

"Community involvement, be it by courage, bravery and/or fancy footwork, helped take a criminal off the streets of Columbus," the police statement said.

"Thank you 'Bill' for sticking your leg out for us."