Lieutenant Colonel Pelonomi Makau said on Saturday an altercation ensued after a 41-year-old man allegedly groped the younger man's girlfriend.
"The incident led to a fight and the 41-year-old man was stabbed with a knife in the neck."
Makau said after the man was stabbed, his friends joined the fight and pelted the 23-year-old with stones. They left the 23-year-old unconscious.
Both men were taken to the hospital, where the 23-year-old was declared dead on arrival.
The 41-year-old was then arrested and is expected to appear in the Koster Magistrate's Court on Tuesday, Malau said.