Two men were shot at a North Side L station during evening rush hour Monday, causing delays on the Chicago Transit Authority’s Red Line.

The shooting happened about 4 p.m. on the platform of the Red Line station at Argyle in the Uptown neighborhood, Chicago police

A shooter entered the platform and “specifically targeted” the men at the station at 1118 W. Argyle St., Chicago Police Sgt. Rocco Alioto said.

A 34-year-old was shot multiple times and critically wounded, Alioto said. He was struck in the back, abdomen, groin and buttocks. Paramedics took him to Saint Francis Hospital in Evanston.

The other man, 41, was grazed by a bullet and declined medical attention, police said.

The shooting was probably targeted against the two men, who were “known to police,” Alioto said. It was unclear how many other people were on the platform. No bystanders were injured.

“We have very good leads at this time,” Alioto said. “Detectives are on scene. They’re interviewing witnesses. They’re looking over the video. Right now we know they were up on the platform [during the shooting].”

Police said they were looking for one gunman.

“The area is heavily saturated in HD crime cameras and detectives are reviewing digital evidence,” police spokesman Anthony Guglielmi said. Area North detectives are investigating the shooting.

The Chicago Transit Authority suspended service to the Argyle station for almost four hours while police investigated the scene.

The CTA initially suspended service near Argyle about 4:15 p.m. for “an unauthorized person on the tracks,” the CTA said. Red Line service was then suspended between Howard and Addison for “police activity.” By 4:45 p.m., Red Line service began moving past Argyle, although trains bypassed the station until three hours later.

Nothing indicated that the shooting was related to another shooting Sunday night in the 5900 block of North Kenmore in Edgewater, Alioto said. In that shooting, a 45-year-old was wounded when two men exited a minivan and shot him in the leg, police said. His condition was stabilized at Saint Francis Hospital.