Tulsa police are unraveling why a man shot four Spartan School of Aeronautics students on Thursday night.

One victim died, and the other three are still in the hospital.

Officers arrested a man about 90 minutes after it happened.

In addition to the man who was killed, one victim was shot in the arm. Another was shot in the arm, but the bullet went into his chest. A third man was shot in the face and the bullet lodged in his neck.

And police said they can't find any real motive.

The Spartan students were in apartment, getting ready to go out for the evening.

Detectives said shooter Mark Hopkins lived in the apartment and is about 20 years older than the other men.

Witnesses said he was drinking, but that it is pretty common.

They say he asked a question, then started shooting.

"The only thing we have is a comment being said by the shooter, aren't you getting ready to go," TPD Sgt. Dave Walker said. "The next thing they know, shooting is occurring."

Police said one of the men had military training and did something quite heroic, by grabbing Hopkins' arm and pushing the gun away.

Hopkins quit shooting and left the apartment, according to witnesses.

"I firmly believe without that intervention, we would've had more shot," Walker said.

Citizens saw Hopkins hopping fences and shedding some clothing, but officers found him shortly after.

He was treated for some cuts on his hands, then booked into jail for first-degree murder.

Police say he's from Alabama and has some sort of criminal past but they didn't have details.

As for the man who died, Chaz Fain, from Florida, one of his friends says he was sweet, kind and encouraging.

"He didn't deserve what happened to him at all," friend Tiffany said. "Out of everybody I know, he probably is the best person who made an impact in my life and my daughter's life."

She said Fain was generous, liked to make people laugh and had plans to join the military.

"I don't know of anybody who does not like him, he's such a sweet and caring guy," she said.

The other victims were from Tennessee, Texas and Illinois.

Police said Spartan school leaders and citizens were both great in helping close the investigation quickly.

An arrest report shows that when questioned, Hopkins reportedly implicated himself as the shooter.