ST. LOUIS — It started out as just another typical morning for Malachi Brown.
"He was on his way to Kay Jewelry in West County Mall. My son worked there for the past six months and he really enjoyed it," said Turkessa Lee, Brown's mother.
The St. Louis mom could not believe the chilling news she received more than an hour later.
"I got a call from him and he was like mom I've been been shot," recalled Lee.
Police said around 10 a.m., gunfire rang out on a Metrolink train at the Maplewood-Manchester station.
Witnesses told police 69-year-old Terry Alexander and the 21-year-old Brown first got into an argument.
"From what I've learned, the beef wasn't with my son. It was between that man and an older woman that he had sneezed on and he got mad about it. The woman got scared and then got off the train and they said he started making indirect comments to my son. They said after he shot him, he went and laid on top of my son," said Turkessa Lee.
Lee said police told her Alexander fired seven gunshots at her son.
Investigators said Brown pulled out his own gun and fired back. They said during a struggle Alexander took Brown's gun.
Brown, hit three times including once in his heart, died at a hospital.
"We're able to see security where we put them," said Kevin Scott, Bi-State Development's General Manager of Security.
Scott said two St. Louis County police officers assigned to the Metrolink Police Task Force were on the second car of the train on Saturday.
Scott said when the train pulled into the Maplewood-Manchester Station, the officers immediately moved to the first car and arrested the armed suspect.
The shooting comes on the heels of two violent fights on East Side Metrolink trains and two attempted rapes on downtown trains.
"We're profoundly saddened by the acts," Scott told 5 On Your Side.
Bi-State Development currently has 150 police and security officers riding its trains, covering 46 miles a day.
Under its $52 million "Secure Platform Plan," the company plans to install new, high security gates to access its platforms, new fencing and add more security cameras at its stations.
"We currently have 38 stations with a 39th to be built at MidAmerica Airport as part of the Secure Platform Plan project. We're moving in the right direction. We're making the system safer," added Scott.
Bi-State Development operates the Metro Transit public transportation system in the City of St. Louis, St. Louis County and in St. Clair County in Illinois.
"I just cannot believe this happened to my son. He just turned 21 in January and had his whole life ahead of him. I just don't know where we go from here. His dad is so torn up that he couldn't even be interviewed today," said Lee.
Construction on Bi-State's plan should start later this year.
In the meantime, suspect Terry Alexander remains in jail on charges of second-degree murder and armed criminal action.
He's being held on a $200,000 cash-only bond.
A GoFundMe has been created to raise money for Brown's funeral expenses. To donate, click here.