Soldiers shot the security guard on Thursday night after he said he would denounce them after they left their barracks in the town of Nzerekore in the east of the country, a member of his family said.
Violence was also reported in several other towns, including Macenta, Kankan, Nzerekore and Faranah.
The trouble began on Wednesday when members of the military who are demanding unpaid salaries totalling about $100,000 began revolting against some of their commanders.
The army has alleged that the authorities have been holding back wages since 1996, the year when one mutiny claimed the lives of 300 soldiers.
Trouble started on Wednesday at the country's largest camp, Alpha Yaya Diallo, situated near the capitals's airport and where Lansana Conte's, the country's ailing president, is situated.
The camp houses elite commando and parachute units, and is also the army headquarters.
On Wednesday night masked soldiers attacked and ransacked the residence of Kerfalla Camara, the army commander.
Calm was reported to have returned Friday to the affected areas.
The rioting by an army that has shored up Conte's rule for years is the first to hit the new government of Lansana Kouyate, Guinea's prime minister, who was appointed in April after weeks of strikes against the regime.