As the city prepares to unveil a new security plan for the CTA, the third tragedy in a month struck the transit system when a man was shot to death and two other people were wounded early Monday in a downtown train station.

The 2 a.m. shooting was sparked by a “personal” dispute but the reason for the argument was unclear, said Anthony Guglielmi, chief spokesman for the Chicago Police Department. He said police were searching for the shooter, whose image was captured on surveillance cameras.

The shooting happened in the tunnel connecting the Jackson Red and Blue lines in the 200 block of South Dearborn.

Crime has been rising on CTA property in recent years, with a nonfatal shooting on a train and a stabbing on a platform also happening just this month.

Guglielmi said a retired Chicago police deputy chief — now the head of security for CTA — has been helping the Police Department design an enhanced safety plan for public transit.

The plan, which will be unveiled in about a week, will include more police manpower on CTA property and improved use of technology to thwart crime, Guglielmi said.

Under a reorganization of the Police Department announced earlier this month, a new counter-terrorism unit will be responsible for policing mass transit in Chicago.

Guglielmi noted that police officers riding CTA trains are now dressed in uniform instead of plainclothes.

“We want their presence known,” he said.

In the Monday morning attack, Edward Charleston, 24, was killed when he was shot in the stomach and chest. Another man was shot in the head and arm and taken to Northwestern Memorial Hospital, where he was in critical condition.

A 19-year-old woman was shot in the back and taken to the same hospital, where she was listed in good condition. Police said she doesn’t appear to have been involved in the argument between the men.

Two babies were in the vicinity of the shooting, Guglielmi said. The children were in the group that included the three victims, but the woman who was shot isn’t their mother, he said.

On Feb. 4, Mike Malinowski, a 26-year-old musician performing in the Red Line station at Jackson, was wounded in a stabbing after a woman attacked him. She said his guitar was giving her a headache, prosecutors said.

Barbara Johnson, 38, of Blue Island, was arrested by police officers at the station and she was identified as the attacker by witnesses and Malinowski, officials said.

Street musician Quron Jackson, 23, who said he knows Malinowski, is taking precautions.

“I try to stay aware of my surroundings always when I am down here,” said Jackson, who was playing guitar in the Blue Line’s Washington station Monday morning. He keeps a close eye on the money people toss his way.

“I try to limit the amount of tips I let be shown after a certain amount in case somebody tries to get an idea.”

The day after Malinowski was attacked, a man was shot in a robbery on the Blue Line at the CTA’s UIC-Halsted stop. Police arrested Patrick Waldon, 31, for allegedly shooting the victim as they struggled over his backpack.

Police released photos of Waldon from CTA surveillance cameras and got “multiple calls from the public ID’ing this individual,” interim Chicago police Supt. Charlie Beck said at a news conference after Waldon’s arrest.

“We also had great cooperation from witnesses at the scene who also identified him,” Beck said. “This is the key to solving crime, particularly violent crime. I am very proud of the people of Chicago for coming forward.”

Police are still seeking a second suspect in that shooting.

UIC student Cara Satoskar said the “transportation system cannot handle” the recent number of incidents. She carries pepper spray and doesn’t take public transportation after 10 p.m.

This year, there have been at least 45 robberies on CTA trains, stations and platforms, according to the city’s crime data portal. Last year, there were 591 robberies on CTA property, the most in five years, the data show.

Overall crime also has been creeping upward on CTA property for the past five years. There were 6,321 reports of crime last year, up from 4,116 in 2015.

There were seven murders over that period on CTA property, the data show.

Contributing: David Struett, Ahlaam Delange

Read more on crime, and track the city’s homicides.