Two people were robbed after responding to social media ads offering phones for sale this month in the South Side Wrightwood neighborhood.
The suspect arranges meetings with victims in the 7900 block of South Whipple Street after they responded to ads, according to a community alert from Chicago police.
When the victims arrived expecting to buy a phone, the man robbed them, police said.
The first hold-up occurred at 12:34 p.m. March 13, while the second happened at 3:10 p.m. on March 21.
The suspect was described as an 18 to 23-year-old man between 5-foot-6 and 5-foot-8, weighing 140 to 180 pounds, police said.
Anyone with information is asked to call Area Central detectives at 312-747-8380.