Cops are searching for a serial bank robber who threatens to start fires and then leaves behind what he claims is a pipe bomb.

Investigators believe the suspect has hit three banks and a credit union in the last six months, most recently robbing a Citibank in Garden City Park Saturday. According the authorities, the man sprays a liquid in the bank and threatens to light it on fire if he does not get cash. Then, police say, he leaves what he claims is a pipe bomb by the door before he leaves.

Police say so far the bomb has been a hoax, but they fear he may escalate the level of violence in subsequent robberies. Anyone with information is asked to call Crime Stoppers at 1-800-244-TIPS.

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