Police have arrested an 18-year-old man who is accused of shooting another man 15 times inside his Missouri home and then hiding his body in a tied-up air mattress, according to court documents.

Jackson L. Pierce has been charged with second-degree murder and tampering with evidence after one of his roommates reported the homicide Monday to St. Peters police, the department announced. A SWAT team staked out the home after the homicide was reported, where they soon arrested Pierce and another juvenile boy who was present.

Pierce also faces a charge of "felony armed criminal action," which is related to the alleged use of the firearm to commit the homicide, according to a complaint.

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Physical confrontation preceded fatal shooting

Pierce is accused of shooting and killing 23-year-old Dalton Coleman and then attempting to stow his wrapped-up body in an upstairs closet, according to St. Peters police.

Coleman had showed up at an address listed in court documents as Pierce's home in St. Peters, which borders Illinois about 100 miles east of Jefferson City, demanding "unknown belongings" and behaving erratically, according to a probable cause affidavit.

The affidavit, written and signed by a St. Peters police detective, stated that a witness who lived at the home had departed that morning before receiving a phone call from Pierce relaying the unfolding confrontation.

The man spoke to both Pierce and Coleman on the phone in an attempt to quell the rising tensions. He also told Pierce to "collect items of value, including a firearm which was kept in a cabinet above the microwave in the kitchen, and store them in his room," the affidavit states.

But minutes later, the witness told investigators that he received another phone call in which he claimed Pierce confessed to fatally shooting Coleman after a physical altercation, court records say. Though the witness claims he implored Pierce to contact the police, Pierce, he said, refused.

Pierce accused of shooting victim 15 times, tying him up in air mattress

After the man alerted authorities himself, St. Peters police responded to the home and began surveilling it for suspicious behavior, the affidavit states.

A SWAT team was later dispatched to the scene and arrested Pierce and another juvenile after using a loudspeaker to order those inside the residence to come outside and surrender.

Investigators obtained a warrant to search the home, where they found a rolled-up air mattresstied tightly and wrapped inside of an upstairs bedroom closet, according to court records. Inside was Coleman's body with a plastic garbage bag secured around his head with a piece of an electrical cord cut from a lamp.

According to the affidavit, Pierce told investigators that he shot Coleman after he forced his way upstairs and attempted to hit him. The first shot struck Coleman in the abdomen, but when he didn't fall down, Pierce admitted that he continued to pull the trigger 14 times until the gun was empty, records state.

Pierce and the other boy then attempted to clean the scene with towels and dish soap, court documents say.

Police recovered the gun at the scene along with 13 shell casings and 12 bullets. Another bullet was found still lodged in the victim's body during the autopsy, which also revealed that Coleman had been shot 15 times in the abdomen, hand and face, according to the affidavit.

Pierce remains in jail with a $1 million bond awaiting his first court appearance, which has yet to be scheduled, court records show.

Eric Lagatta covers breaking and trending news for USA TODAY. Reach him at [email protected]