A defendant in a high-profile Oklahoma murder case was found dead in a Tulsa home following an overnight standoff, police said Tuesday.

Allen Shields died overnight of an apparent suicide after releasing his ex-girlfriend's 11-year-old daughter who he had held hostage for almost six hours Monday evening, KRMG reported.

Tulsa police officer Leland Ashley said Tuesday that officers entered the property in the 5000 block of North Utica Place after hearing gunshots.

"We used precautions before we made any type of entry. We actually used chemical agents, pepper balls outside the residence to attempt to get a response. We were unable to get any type of response," Ashley said.

Shields had barricaded himself inside the home of his sometime-partner, Sherrell Dumas, shortly after 5:00 p.m. local time Monday, holding her daughter hostage.

He released the girl unharmed shortly before 10:30 p.m., but remained holed-up inside the house, which the police had surrounded.

It was the second time in 14 months Shields had taken the girl hostage, KWTV reported, with authorities alleging on the earlier occasion that Shields had a "homicide starter kit" with him that included a gun, handcuffs, and sleeping pills.

Shields was scheduled for a court appearance Monday afternoon on charges relating to the murder of businessman Neal Sweeney, but failed to show up. He pleaded guilty to a conspiracy count last year and was free on bond.

Prosecutors alleged that Shields and three others were involved in a murder-for-hire plot against Sweeney.

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