Tucson police spokesman Chris Widmer says officers around 12:45 a.m. found a 31-year-old man who had been shot inside a home and pronounced him dead at the scene.
Widmer says two other adults in the home were unharmed.
Investigators say the suspect showed up at the house and got into an argument with the victim at the front door.
They say the suspect then fired through the door, hitting the victim.
Widmer says both men were acquainted but police are still working to confirm the suspect's identity.
Anyone in the area with information is asked to call 911 or 88-CRIME.
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