Police arrested 39-year-old William Johnson of the 400 block of Morris Street Friday afternoon.
Police were called to a bar in the 200 block of S. Camac Street at 11:34 p.m. Thursday for a report of a stabbing.
Once there, police found two victims - the off-duty officer and a friend.
Residents and merchants in the neighborhood say they have been having increasing trouble with street hustlers.
Last night, one of them lashed out with a knife, wounding two people, including an off-duty cop who patrols the neighborhood.
"There was a gentleman hanging around the area coming back and forth all day," said Jeffry Shaw.
Jeffry Shaw is the chef at the Venture Inn.
He says a guy known on the streets as "Billy" had been hanging around outside the bar for hours.
The bar hosted a comedy show Thursday night and the police officer, who patrols the neighborhood, showed up with some friends.
Police say the two were walking to another bar when they were approached by the suspect, now identified as Johnson, who allegedly demanded money and cigarettes.
The off-duty cop identified himself as a police and told the man to leave them alone.
Johnson allegedly swore at them then attacked, fighting with the officer.
During the fight, the officer was stabbed four times.
The bartender, Tommy Martinez, tried to break it up and got a deep gash on his chin.
He says he managed to throw the knife into a stairwell after Billy dropped it.
He and the officer went back inside the bar after Billy ran off.
"I think he was more in shock," said Shaw. "I went into the bathroom with him and when he lifted up his shirt, he had a stab here and a stab here, and a couple on his legs."
The 49-year-old officer then walked with the bartender a few blocks to Pennsylvania Hospital.
Police are not releasing his name, saying only that he has been on the force for 19 years.
He is currently listed in stable condition.
Martinez declined an on camera interview when he returned to work Friday.
His manager says he is just glad no one was more seriously hurt.
The chef says, until now, the street hustlers around there had been mostly non-violent.
"There's a few of them in the area all the time walking around begging for money or cigarettes," said Shaw.
Police say Billy Johnson has gone from being a nuisance to a dangerous criminal. He is facing assault and attempted murder charges.