A man who instigated an argument was shot Wednesday afternoon in the Lincoln Park neighborhood, officials said.The 34-year-old was “exhibiting erratic and dangerous behavior” when he approached a group of people near a sidewalk about 4 p.m. in the 2400 block of North Clark Street, causing an argument, according to Chicago police and Ald. Timmy Knudsen (43rd).Another man pulled out a gun and fired shots. The 34-year-old was struck in his chest and taken to Advocate Illinois Masonic Medical Center, where he was listed in critical condition, police said.The gunman fled the scene.Knudsen, whose ward covers the area where Wednesday’s shooting occurred, said there would be heightened police presence in the area throughout the night.“There is reason to believe this is an isolated incident wherein the victim and offender had a preexisting relationship; however, it is currently being fully investigated by the 19th District police and Area 3 detectives,” Knudsen said in a statement.