The Correctional Service of Canada says Martin Pinkus was discovered unresponsive in his cell Wednesday at Drumheller Institution.
Staff tried to resuscitate the 47-year-old man and emergency services were called, but he was pronounced dead at the local health centre around noon.
Pinkus had been serving time since December 1999 for second-degree murder, aggravated assault and assault causing bodily harm.
There was no immediate word on the cause of death.
On Monday, Drumheller staff found a convicted murderer, Earl William Davenport, unresponsive in his cell and could not revive him.
The 56-year-old man had spent more than 25 years in prison for killing two women in Hamilton in 1986.
A Correctional Service spokesman says foul play is not suspected in Davenport's death.
Also on HuffPost