MISSOULA, Mont. -

Police still have not made an arrest after a man was fatally shot in a Missoula strip club parking lot. Officials are looking into whether it was self-defense.

Police say the 27-year-old Missoula man who reportedly fired the gun is still cooperating with the ongoing investigation.

The incident occurred after the 23-year-old victim and the alleged shooter got in a physical fight in the parking lot.

The Missoula County Sheriff's office says Christopher Michael Hymel, of Louisiana, was shot and later died in the hospital.

On Tuesday, police told NBC Montana they are exploring every possibility in their investigation, including self-defense.

NBC Montana talked with Mat Stevenson, a criminal defense attorney who has been practicing law in Montana for 12 years. He explained the laws for defending yourself.

He showed us the Montana codes. There are two words that are at the heart of the law: "reasonably" and "justified."

Montana law uses those words to describe the amount of force a person reasonably can use to justify self-defense.

"There’s no absolute formula that you could refer to, that you could say what's justifiable in any given case," said Stevenson.

Two and a half pages of law govern the use of force.

"The reason why there is so little law on it is because the idea of what's justifiable is typically left up to a jury. A jury gets to decide in any given situation whether force was reasonable or not," said Stevenson.

Missoula investigators tell NBC Montana they're still examining what happened before, during and after a Missoula man fired a fatal shot at a Louisiana man outside a Missoula strip club on Labor Day. So far, the shooter is free.  No charges have been filed.

"Every little fact can weigh in on whether use of force is justifiable or not. Any little factor. Something as simple as whether the person who pulled the trigger was in the process of getting into their car when they did it when they pulled the trigger or whether they were actually opening the door and in the process of getting out. That fact or that distinction of facts could be easily the difference between whether a jury finds someone guilty or not guilty in a jury trial," said Stevenson.

Investigators won't know what they have until all available evidence is collected.  Then it will be up to prosecutors to sift through what investigators found before deciding if the case will go to court.

The police department wants information from anyone who may have witnessed the shooting. You can call Detective Mitch Lang at (406) 552-6292 or Detective Bob Franke at (406) 552-6643.