SIOUX FALLS, S.D. (AP) — Authorities say a 33-year-old Sioux Falls man accused of stabbing his girlfriend's male roommate has turned himself in.

The Argus Leader reports John Sheffield surrendered to police Thursday morning after a $20,000 warrant for his arrest was issued Wednesday. He's charged with aggravated assault in the March 7 stabbing of a 34-year-old man.

Police spokesman Sam Clemens says the victim shared an apartment with the Sheffield's girlfriend. He says the victim's girlfriend told police the four of them were in the apartment when Sheffield walked up to the victim and began stabbing him in the neck.

It's unclear what caused the altercation, but the men had reportedly been drinking.

Clemens says the victim's condition has improved since the attack. It wasn't immediately clear if Sheffield has an attorney.

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