Idris Abdulgani pleaded guilty Friday to second-degree murder in the 2016 killing of Lonnie Leafloor.
Abdulgani, 22, was originally charged with first-degree murder last October.
Leafloor was found dead in his apartment at 1400 Lepage Ave., an Ottawa Community Housing building, on May 2, 2016. He had been stabbed.
His family said Leafloor, 56, had struggled with addiction, and believed his death was likely drug-related.
Randy Leafloor told CBC News his brother was worried about his safety after a fight that took place about two weeks before his death.
"It was all about drugs. This individual put a knife to his throat and threatened to kill him," Randy Leafloor said. "Since then he was walking around with a screwdriver because he was very scared this guy was going to come back to kill him."
Seen in victim's apartment
According to the agreed statement of facts for the guilty plea, Abdulgani had been seen at Leafloor's apartment on April 29, 2016, both by friends and on video surveillance.
Abdulgani was arrested and jailed on May 2, 2016 for allegedly assaulting a taxi driver.
Further evidence of Adbulgani's involvement in Leafloor's death came to light when police met with his cellmate at the Ottawa-Carleton Detention Centre, the statement says.
The jailhouse informant told police Abdulgani had confessed to killing Leafloor.
He told police Abdulgani said Leafloor owed him money because of diluted pills, and that he was tired of being "punked."
Stabbed with steak knife
Adbulgani told the informant he was with Leafloor in his living room and gave him 30 milligrams of hydromorphone, an opioid sold under the brand name Dilaudid.
He then took a steak knife from Leafloor's kitchen and stabbed him in the throat, pinning Leafloor down with a chair when he tried to fight back. Abdulgani stabbed Leafloor several more times.
Abdulgani then washed his hands, put on his shoes, took some money Leafloor had hidden in a sock and left the apartment, according to the statement.
Forensic specialists matched Abdulgani's DNA profile to various items in Leafloor's apartment, including a straw from a McDonald's cup and a blood-stained cigarette butt.
Abdulgani was arrested and charged with Leafloor's murder after pleading guilty to robbery in another matter.