Still, the situation does have some local passengers on-edge.
"It's pretty terrifying, but we rely on the CTA to get all over the city," said CTA passenger Tyler Banaszak.
Former FBI Agent Ross Rice told FOX 32 because surveillance cameras were reportedly down in that station where the attack happened, cell phone video from passengers and passers-by will be key in the investigation.
"If you think back to the Boston Marathon bombing, it was social media and the public that came froward with videos that eventually led to the arrest of the two brothers that committed that attack," said Rice. "I think the same thing is going to be important here."
The CTA said there are no reports of any threats against its system.
Meanwhile, Metra's Michael Gillis said in a statement: "We remain as vigilant as ever about safety and security issues, and, as a precaution, we have deployed additional resources today. And we would remind and encourage our riders and the public that if they see anything or anyone suspicious to report it to Metra police...if you see something, say something."
"I think there's always a little bit of risk taking the CTA, but it doesn't affect my mind too much," said CTA passenger Ian MacKimm. "I'll still be taking it."
"I think people are going to be more aware, but I don't think we will see any drop in commuters," said Banaszak.
The Chicago Police Department told FOX 32 officers are "maintaining appropriate resources" to keep Chicago trains safe.
At least 28 people were injured, 10 of them by gunfire, in a subway car in Brooklyn after a man released a smoke canister and opened fire, New York City officials said Tuesday morning.