Boston Mayor Thomas M. Menino took a hard line this morning when asked about the surviving suspect in the Boston Marathon bomb attacks.

"I hope that the US Attorney takes him on the federal side and throws the book at him," Menino told ABC's "This Week" program. "These two individuals held this city hostage for five whole days."

Dzhokhar A. Tsarnaev, 19, of Cambridge, remains hospitalized in serious condition at Beth Israel Deaconess Medical Center, where he was taken Friday once he was in police custody.

The mayor also said that information he has indicates the brothers acted on their own.

Menino said he agreed with the move to put Boston and other nearby communities on lockdown Friday, adding that officials discovered an explosive device not related to the Marathon attacks.

"At that time we found a pipe bomb at another location in our city of Boston," he said. "Another individual was taken into custody."

Tsarnaev and his older brother, Tamerlan, were involved in a pursuit and later firefight with law enforcement officers late Thursday and early Friday. With wounds from both gunshots and blasts, Tamerlan Tsarnaev was taken to Beth Israel early Friday, where he was pronounced dead shortly thereafter.