About 50 people narrowly escaped death on Saturday at the Matsieng Airfield a few kilometres north of the country’s capital Gaborone.
It is understood that the man had had a physical altercation with his wife at a baby shower held at the airstrip before he was chased away.
He allegedly stole the aircraft and crashed it into the party venue.
Viljoen started work at Botswana-based Kalahari Air Services in October last year.
In a statement, the Matsieng Flying Club said an uninvited guest at a party, who was identified as Viljoen, got into a domestic dispute before leaving the venue.
Minutes later, a King Air twin-engine aircraft allegedly stolen by Viljoen started making several low passes.
A man said that the pilot called his friend who was at the venue.
“He phoned his one mate on the ground there who was still at the party and he wanted to know where his wife was. The guy that he called started shouting so that everybody could run away. And then he flew into the Matsieng clubhouse.”
Viljoen was the only casualty, while the clubhouse, control tower, and about 13 vehicles were destroyed.
The police and Botswana aviation officials were investigating the incident.