Lake County sheriff's officers are investigating the armed robbery of a Knollwood gas station Saturday.

Sgt. Christopher Thompson said a man entered the Knollwood Marathon around 6 p.m., demanded money from the clerk on duty and fired one shot into the floor from what appeared to be a .380 caliber semiautomatic pistol.

The robber then demanded a pack of cigarettes before fleeing south on foot. A search of the area failed to turn up the suspect.

Thompson said the man was described as 40 to 45 years old and was wearing a brown leather jacket at the time of the robbery.

Anyone with information is encouraged to call (847) 377-4250.