A 34-year-old Illinois convict was convicted Thursday in the beating deaths of four people with a hammer, the Associated Press reported.

Nicholas Sheley, who is already serving life sentences for two murders, was convicted for beating three adults and a 2-year-old child to death with a hammer in June 2008. Police say Sheley committed the murders and other crimes during that summer starting in his hometown of Sterling all the way to St. Louis. The four murders were committed at an apartment in Rock Falls.

It took the jury just over three hours to find Sheley guilty for the deaths of 20-year-old Kilynna Blake, her 2-year-old son Dayan, Brock Branson, 29, and Kenneth Ulve, 25.

"Nicholas Sheley is the one responsible for these murders," Assistant Attorney General Steve Nate said, the AP reported. "Nicholas Sheley killed Brock. He killed Ki. He killed Dayan. And he killed Kenny."

Prosecutors say Sheley committed the murders because he thought his ex-wife, Holly Sheley, was having an affair with Branson.

Holly Sheley testified that she and Nicholas had sex in a pickup truck the night of the murders, the AP reported. The back of the truck was filled with blood.

Surveillance cameras caught Nicholas Sheley walking around wearing clothes belonging to one victim a few days after the murders. Investigators also found his DNA at the crime scene.

Sheley is currently serving two life sentences for the June 2008 killings of 93-year-old Russell Reed and Ronald Randall, 65, whom were murdered several days before he butchered four others with a hammer.

Reed was found dead in the trunk of Sheley's car in Sterling, 110 miles west of Chicago, the AP reported. Police say Sheley killed him in search of money to buy cocaine. Sheley killed Randall five days later and stole his truck, the same one he and his wife had sex in the night of the four murders.

Sheley is scheduled for his next sentencing on Aug. 11. He faces an upcoming trial for the murders of an Arkansas couple in Missouri.