The arsonist who set alight the Pennsylvania governor’s mansion while his family slept inside planned to beat Josh Shapiro with a sledgehammer.

Cody Balmer, 38, pleaded guilty to a number of charges on Tuesday including attempted murder, terrorism and arson for the April 13 attack which caused millions of dollars worth of damage to the state-owned brick building in Harrisburg.

Under a plea deal, Balmer was sentenced to 25 to 50 years in prison.

Mr Shapiro and members of his family were awakened and evacuated from their burning home shortly after they celebrated the Jewish holiday of Passover with a Seder in the residence. No one was injured.

Balmer scaled an iron security fence in the middle of the night to carry out the attack and used beer bottles filled with gasoline to ignite the property.