Christopher Gratzinger

An alleged knife-wielding robber is behind bars, thanks in part to a good Samaritan, authorities said.

Christopher A. Gratzinger, 30, who has no known address, was captured Tuesday night at a house in Butler Township.

Butler police had been looking for the heavily-tattooed Gratzinger since about 10 p.m. Monday, when they say he held up a convenience store at knifepoint and made off with money and cigarettes.

He is accused of pulling the knife on a clerk at the 7-Eleven on Pillow Street under the guise of buying an iced tea drink. He demanded all the $20 bills, police said.

When the clerk advised him there were no 20s, according to court documents, he reached over the counter and removed all the money — $25 — from the register.

He also grabbed two packs of Newport 100 cigarettes.

He left the store but police did not indicate if they believe he had a getaway car waiting for him.

Police reviewed surveillance video and immediately identified Gratzinger, who has tattoos on his face, neck and body.

City officers also have arrested Gratzinger, a repeat felon, for prior crimes including a snatch-and-run robbery last year at another convenience store.

State police and other departments began searching for Gratzinger Tuesday afternoon, but to no avail.

Enter the good Samaritan.

Investigators said a motorist traveling Route 68 in the Chicora area about 9 p.m. Tuesday stopped to give a ride to a hitchhiker, unaware it was Gratzinger.

He asked to be taken to an acquaintance's home in Butler Township. The driver, who authorities did not identify, obliged.

But the hitchhiker's appearance — shoeless and dirty — raised the good Samaritan's suspicions. He immediately drove to the nearby state police barracks and reported what had occurred.

It happened that a Butler Township police officer was there as part of an unrelated investigation. When the man described the hitchhiker, the township officer knew it was Gratzinger and notified city officers.

Police from both departments went to the home and arrested Gratzinger, investigators said, but not before he tried to run out the back door.

He was arraigned on charges of robbery and possessing an instrument of crime. He is being held in Butler County Prison on $75,000 bail.

Butler police Deputy Chief David Adam on Wednesday said the robbery investigation is ongoing.

Gratzinger, meanwhile, is already awaiting trial in four separate criminal cases, including the July 21, 2017, robbery of the E-Z Stop store on North Main Street in Butler.

Police said in that snatch-and-run robbery he stole a carton of cigarettes.

Court records show that Gratzinger has four prior felony convictions.