Sawyer Robison, 27, had previously been charged with two counts of attempted murder and 15 weapons charges in connection with the Feb. 7 shooting of RCMP constables Sheldon Shah and Sidney Gaudette.
Robison's uncle Bradford Clark was found dead in the house after the shootout.
Robison was arrested in Feburary on the attempted murder charges.
The murder charge was filed Monday.
"I can't say very much except to say I'm very surprised with this development," said his lawyer, Brian Beresh.
Police searched for Robison for three days after he was spotted leaving the scene. He was arrested on a rural road after a public plea from his parents to turn himself in.
Robison was granted bail in June on the attempted murder charges and had been complying with his conditions, Beresh said.
News of the new charge caught some in the town of Killam off guard.
"I’m quite surprised that he has been charged with murder. But we always suspected there was something else to make the big Canada-wide manhunt," said Ron Christensen, who has lived in the town for two decades.
"The manhunt started so fast, for something we thought Sawyer could not have done."
Christensen says rumours have been swirling around the case since the shooting, but very few people know what to make of what happened.
“We don’t have any answers. Nobody has.”
Robison is scheduled to appear in the Wetaskiwin Court of Queen's Bench on Oct. 30.