CHICAGO >> A Chicago man who gunned down five of his neighbors over the weekend had had angry run-ins with his fellow tenants and left threatening notes on the inside of his door suggesting he was planning an act of violence, authorities said today.

Investigators haven’t determined the exact reason why 66-year-old Krysztof Marek allegedly shot his neighbors on Saturday. According to police, he shot four of them as they were sitting down for dinner and then entered another woman’s apartment, shot her in the abdomen and then followed her as she fled out of her back door and shot her in the head.

During a hearing today in Cook County Circuit Court, prosecutors said they found two threatening notes written in Marek’s native Polish language that were taped inside the door of his northwest side apartment.

One of the notes read: “No mercy. Remember whatever s—- they do to you, you control it yourself, not them. Enough. They have to pay for it.”

The other read: “Tomorrow, No mercy without any stupid hesitation. Remember who you are. Remember what this piece of s—- is doing to you. Enough.”

Police spokesman Anthony Guglielmi said Marek had previously confronted his neighbors over what Guglielmi described as petty matters, including telling off a woman who angered him because he felt she was walking too loudly on the floor above his apartment. And in a court document, prosecutors said the condominium association was seeking to evict Marek because he had failed to pay his mortgage and other fees.

After the shootings, Marek put the .40-caliber handgun on a coffee table in his apartment, walked outside and told police when they arrived, “I think you’re looking for me. I did it,” according to the document prepared by the county’s state’s attorney’s office that was read aloud by a prosecutor at today’s hearing.

Marek faces five counts of first-degree murder, and the judge ordered him to remain jailed without bond.

The county medical examiner’s office has identified the victims. The four people shot inside the apartment were 43-year-old Kostadinova Tsvetanka; her 43-year-old husband, Ivaylo Popov; 61-year-old David Hanik; and 65-year-old Iskra Pourel-Popova. The woman who was shot in the head as she tried to flee was identified as 53-year-old Jolanta Topolska.

Guglielmi said all of the victims knew Marek and that at least some of them were Polish.