An eyewitness told the Eastleigh Voice that the first-year student identified as Halima Hajir Abdullahi was in the company of other women at Galmagala's Town center when the reservist reportedly appeared from nowhere and fired one shot.
The bullet, according to witnesses, entered through her chest, killing her instantly in an incident that shocked locals in the area.
After the shooting, the assailant who is said to be a National Police Reservist working in Deka Harja fled the scene but later surrendered to the police.
Fafi Deputy County Commissioner Thomas Bett said the suspect is being processed and would be arraigned.
He said the motive of the killing is yet to be established. He regretted that the young girl was pursuing teaching and she would have been an asset to the community that is grappling with the shortage of teachers.
Bett confirmed that the body of the college student was brought to Garissa referral hospital for postmortem before she was buried according to Islamic rites.
The girl who has been described by her classmates as charming, lovable, and friendly was to report to the college on Monday.
"She was nursing her elderly and sickly grandmother and she was to report to the college today," Abdi Abdullahi, a Galmaga resident said.
Following the news of her demise, Garissa Teachers College where the deceased student studied was thrown into mourning.