The crime has shocked Hallin's neighbors and friends.
Just steps from the Southwest Side home where the man everyone on the block called Bill lived alone, stunned neighbors gathered as they learned with disbelief that Hallin was murdered.
"He was the kind of neighbor you want. I'm totally shocked. I can't believe someone would do this to him," friend Debbie Sanzma said.
It was Friday night after firefighters responded to calls for help when most learned the 67-year-old had been set on fire and found dead at a South Side property he owned.
Police immediately began a death investigation, and neighbors say a second-floor tenant was taken into custody.
However, detectives have yet to release a motive for the crime or confirm that a suspect is in custody.
"The guy had been causing trouble around here for a while -- shot windows out of cars over there with a bb gun," neighborhood resident Matthew Murphy said.
Friends of the victim who asked not to be identified say Hallin recently accused his upstairs tenant of only two months of stealing some of his work tools, and that on the day he died, possibly confronted the man after being called to the apartment because of several complaints from the neighborhood.
"It's despicable. It's arrogant. It's rude. People these days, I just don't know what to say. I mean, it's hard," a person who wished to remain unidentified said.
It's especially difficult for this close-knit community of neighbors who have become friends.
This afternoon, they remember Hallin as a gentle man, while they struggle to accept his violent death.
"To do him like that, I don't understand it. He was a good neighbor," neighbor Deborah Bell said.
Investigators are still awaiting autopsy results that they hope will tell them the exact cause and manner of Hallin's death.
At this hour, police officials are still not confirming if there are any suspects in custody, but do say there have been no arrests.