BOSTON (CBS) – The FBI is searching for a repeat bank robber they've dubbed the "Spelling Bee Bandit" because of a recurring error in the notes he leaves tellers.

The man was captured on surveillance camera robbing TD Bank locations in Arlington, Reading and Peabody and a Salem Five Bank in Burlington over a two-week period beginning October 31.

In each robbery, the unknown suspect wrote "robery" on the back of a withdrawal slip and passed a demand note to the teller.

According to the FBI, the man has "become more aggressive with the tellers" in each subsequent incident.

The man is described as 5'11"-6'2" with a slim build, likely in his late 30s or early 40s.

The MassMostWanted Tip Program is offering a $1,000 reward for information leading to the man's arrest.