Hattar was struck by three bullets before the assailant was arrested, said Petra. Witnesses told AFP that a man had opened fire in front of the court in Amman's Abdali district.
The 56-year-old Christian was arrested on August 13 after posting a cartoon mocking jihadists on his Facebook account.
He was charged with inciting sectarian strife and insulting Islam before being released on bail in early September.
Jordan's attorney general had imposed a blackout on media coverage of the case.
Jordan is a leading member of the US-led coalition fighting the Islamic State group in neighbouring Iraq and Syria, and was the target of a June 21 suicide bombing that killed seven border guards.
The kingdom has carried out air strikes targeting IS jihadists and hosts coalition troops on its territory.