WILKES-BARRE, Pa.—A man was arrested immediately after his release from state prison Friday on a charge that he plotted to kill a key witness against double murder suspect Hugo Selenski.

Thirty-nine-year-old Michael J. Scerbo was charged with solicitation to commit homicide.

Authorities say Scerbo offered $1,000 to an undercover state trooper to kill Paul Weakley, who's serving a life sentence on charges related to the 2002 homicides of Michael Kerkowski and Tammy Fassett in Luzerne County.

Weakley is expected to testify against Selenski, who is charged with killing Kerkowski and Fassett. Their remains were unearthed from Selenski's back yard in 2003.

It's not clear whether Selenski had anything to do with the alleged plot. He is serving a 32-year sentence for robbery.

Prosecutors didn't return a phone call.