A 70-year-old Chicago Transit Authority worker was attacked and thrown onto the Blue Line tracks in the West Loop Thursday morning.

CBS News Chicago has learned the man was a 27-year veteran of the CTA. The union representing CTA workers is now pushing for more security.

Calls for help came in around 7 a.m. Thursday after the CTA customer service agent was attacked at the Grand Blue line station, in the subway beneath the six-way intersection of Milwaukee and Grand avenues and Halsted Street.

The customer service agent had left the booth, and police said a man punched him and then shoved him onto the tracks.

CBS News Chicago's cameras were rolling as police responded.

"A passenger threw him onto the tracks," said Pennie McCoach, president of the Amalgamated Transit Union (ATU) Local 308. "A Good Samaritan and other customers and a coworker assisted him off the right of way off the track."

McCoach, currently out of state at a conference, broke down the details of the incident Thursday morning virtually.  She said the 70-year-old man who was attacked is kind and would never start a fight.

"For this to happen to him? This is mind-boggling," said McCoach.

The CTA employee was transported to Northwestern Memorial Hospital with minor injuries.

"I'm not sure what took place as to why the customer felt he needed to punch him in his face," McCoach said.

McCoach said it was unclear why the CTA worker left the booth to help the customer who ended up attacking him. But she said the union is now advising all members to stay in the booth during their shifts.

As for the man behind the attack, he ran away. But Chicago police said they tracked him down Thursday afternoon, and he was taken into custody.

Meanwhile, McCoach said workers are calling for increased safety and security measures following this incident. The union is too.

"I've been advocating for a dedicated police force," McCoach said.

McCoach said the CTA employee was not seriously physically injured. But she said all CTA workers are calling for increased safety measures following the incident.

"The employees are enraged. The employees are afraid," McCoach said. "The employees don't want to engage with the public because they don't know what they're going to run across because of situations like this."

Power was cut at the Grand station, and trains were halted for some time following the attack.

The CTA released this statement:

"CTA's close collaboration with the Chicago Police Department (CPD) has led to the swift arrest of the individual who assaulted a CTA employee at the Grand Blue Line station this morning. The offender was apprehended through the use of the recently expanded CTA Strategic Decision Support Center — a CPD facility where officers use real-time feeds from thousands of CTA cameras to relay information to officers in the field."