Officers and first-responders found four people with gunshot wounds inside the house.
Three of the victims were found dead at the scene. The fourth person was hospitalized with a non-life-threatening gunshot wound to his foot, police said.
The fourth person, identified as 20-year-old Alexander Ken Jackson, was arrested on three counts of first-degree murder after he was released from the hospital.
Police identified the deceased as Jan Jackson, 61; Melissa Jackson, 68; and Sabrina Jackson, 19; and said they were the father, mother and sister of the suspect. All three victims had been shot to death, police said.
A .22-caliber Browning semiautomatic rifle found in the house was believed to be the murder weapon, police said.
The Cedar Rapids Gazette reports Alexander Jackson was the person who called 911 to report the shooting Tuesday morning. Jackson said a male intruder had shot him and his father.
The victims were each in different rooms in the house, the Gazette reports, citing court documents.
Jackson reportedly told police he was awakened by the sound of gunfire, and said he was shot in the foot in a struggle with the purported intruder, the Gazette reports. Jackson has no previous criminal record, the paper reports.
No evidence of a break-in was found at the house, police said.
“The defendant denied shooting his family members but admitted his father had recently advised that he needed to find a job or move out of the residence,“ the criminal complaint stated, according to the Gazette.