LINCOLN -- The city's 5th knife point convenience store holdup in the last month has police wondering if they are related. Robbery No. 5 happened around 8:30pm Wednesday at Casey's General Store, 550 West Cornhusker. A man with a 3 to 4 inch knife demanded money. The search is on for a 6-foot tall black man with a lighter complexion, wearing a black t-shirt. Lincoln Police Capt. Jason Stille tells KFOR NEWS it's too soon to say the 5 knife point robberies are related.