A person was found dead Saturday afternoon in southwest suburban Oak Lawn after police responded to what they initially described as a barricade situation.

About 8:20 a.m., officers arrived to the 10400 block of South Mason Avenue after receiving a call from someone saying they were concerned a family member may hurt himself or others, according to Oak Lawn police.

When they arrived, officers and a witness heard what sounded like a gunshot come from inside a residence, police said.

Officers evacuated the area and established a large police presence in the area bounded by between 103rd and 105th streets and Austin and Central avenues, police said. Authorities weren’t able to make contact with anyone inside for several hours.

The South Suburban Emergency Response Team eventually deployed a drone with a camera that showed a motionless male inside, police said. Authorities forced their way in and found him dead, police said.

Grid View Police respond to a reported barricade situation June 29, 2019, in the 10400 block of South Mason Avenue Justin Jackson/Sun-Times

Police respond to a reported barricade situation June 29, 2019, in the 10400 block of South Mason Avenue Justin Jackson/Sun-Times

Police respond to a reported barricade situation June 29, 2019, in the 10400 block of South Mason Avenue Justin Jackson/Sun-Times

An autopsy was scheduled for Sunday at the Cook County medical examiner’s office.

Police initially thought they were dealing with a “barricade situation,” warning residents in a tweet about 10:30 a.m. to stay indoors as units investigated a barricaded subject.

They tweeted that the situation was under control around 2:30 p.m., about four hours later.

Mason Avenue was expected to remain closed between 104th and 105th streets into the evening.

This is a developing story. Check back for updates.