By Jeremy Ross

(CBS) – The suspect in a Sept. 6 pipe bomb explosion in East Chicago, Ind. could be behind another threat directed at neighboring Hammond.

Hammond Mayor Thomas McDermott says the pipe bomb that exploded at the East Chicago post office last month, injuring a worker, was meant for an attorney working for the city. He says the same person who sent the package is believed to have sent a manila envelope to a city worker at the employee’s home. The envelope, delivered Friday, contained threats, the mayor says.

“It was a creepy threat,” McDermott tells CBS 2’s Jeremy Ross. “Anybody would be scared by this threat.”

bomber East Chicago, Ind. Post Office Bomb Linked To Hammond Threat

Sketch of suspect who set off a pipe comb at the East Chicago post office earlier this month. (FBI)

McDermott says law enforcement is certain both incidents are connected.

The FBI previously released a sketch of a person of interest in the East Chicago post office bombing.