4:30 a.m. Friday update:
We spoke with Green Bay police, no one has been taken into custody in connection with a murder on Green Bay's east side.
Steven Sims was shot Tuesday night on Stuart Street.
GREEN BAY - Green Bay police revealed new details Thursday in a homicide investigation.
Investigators say they are looking for 21-year-old Terry Shepard. They consider Shepard, who just got out of prison, armed and dangerous. Police describe him as a person of interest in the shooting.
There is a nationwide warrant out for Shepard's arrest. This stems from an incident late Tuesday night on Stuart Street.
Police say 32-year-old Steven Sims was shot and later died at a hospital.
Investigators say Shepard may be in the Green Bay area, but does have ties to the Kenosha area.
Investigators are asking Shepard's friends, family, and the public for help finding him.
Police say Steven Sims was shot inside a lower apartment at 1144 Stuart St. during an encounter with Terry Shepard.
"The information we have at this time is that Terry Shepard had a handgun and shot at Mr. Sims," said Green Bay Police Captain Todd Thomas.
During a press conference Thursday, investigators say the situation quickly unfolded after Sims arrived at the house.
"It was very brief. He was at the house for a very short period of time before the incident," Thomas said.
Investigators describe the incident as a targeted attack.
Police say Sims came to Green Bay from the Chicago area a couple of years ago, and was dating a woman who lived at the apartment.
"They recently had been having problems in the relationship and he had not been staying at that address," said Thomas.
Police say the woman is Shepard's ex-girlfriend.
FOX 11 spoke with her when she stopped by the house to pick up some belongings. She did not want to go on camera, but said Terry Shepard was invited to the house. She was not expecting Sims to show up.
The woman would not say what led up to the shooting, but says the two men were not fighting over her.
As the search for Shepard continues, investigators say they've found the handgun believed to be used in the homicide.
However, public safety is still a concern.
"That doesn't mean he doesn't have access to other weapons. He was in prison for quite a long time," Thomas said.
Court records show in 2010, Shepard was convicted of several charges, including battery and theft.
Police say Shepard was released from prison on April 7. He arrived in Green Bay on the day of the incident.
"Our main concern now is to safely locate him and safely take him into custody," said Thomas.
Again, police say Shepard should be considered armed and dangerous, and the public should not approach him.
If you have any information or see Shepard, call Green Bay police at (920) 448-3200.