From the April 15, 2004 Lowell, Massachusetts Sun:
WILMINGTON A knife-wielding robber fled empty handed but unharmed after his victim pulled a gun on him Sunday night, according to police.
The unidentified man went into Forest Service Center at 316 Lowell St. about 8:15 p.m. asking for change to use in a vending machine, Police Chief Bernard P. Nally said.
The clerk left the office to tend to a customer and when he returned the man asked for more change.
"After the attendant made change the second time the suspect produced a knife and pointed it at the attendant and said, 'Don't do anything stupid and give me all the money,'" Nally said. "About this time the attendant produced a handgun which he is lawfully licensed to do and ordered the suspect to leave the store, which he did."