A resident of the building, on the 8600 block of Shermer Road, told Niles police she walked in on the couple having sex on a chair in the lobby around 5:30 p.m., March 26.
Police said the 44-year-old woman yelled at the teenage boy and girl to stop what they were doing and leave, but when the boy stood up he pushed the woman into the wall.
“But we don’t have any place to have sex,” he reportedly told the woman.
The couple then ran out of the building and were last seen heading south on Shermer, police said.
Niles officers checked the area, but were unable to locate the couple.
The boy was described as between 16 and 18 years old and wearing a black sweater, while the girl was about 16 to 17 years old and was wearing a pink blouse, according to police.
The woman who walked in on the couple was planning to talk to the condo’s board about having a security camera installed in the lobby, police said.