MANKATO, Minn. — Alcohol, jealousy and misplaced anger were the kindling for an explosive fight that left a former Minnesota State University football player with permanent injuries and likely ruined the Division I career of a former University of Minnesota football star.

The fight between Isaac Kolstad, a former North Dakota State and Minnesota State University linebacker, and Philip Nelson, a former Gopher quarterback, started in Mankato’s downtown entertainment district at bar closing time on May 11. Nelson and another man, Trevor Shelley, 21, of St. Peter, are facing first- and third-degree assault charges stemming from the incident.

Witness interviews with police recently became public when they were entered into evidence at a court hearing for Nelson. They describe many of the events leading up to the assault, which left Kolstad with a skull fracture and a traumatic brain injury. Kolstad has since undergone months of treatment and physical therapy to recover from his injuries.

Nelson, who is 21 now but was 20 at the time, had been drinking in two downtown Mankato bars with his underage girlfriend, Malorie Veroeven, 19, Nick Kaus, 22, Sam Thompson, a former teammate, and other friends before the argument started. Thompson and Kolstad had been at the same two bars, Blue Bricks and South Street Station, but hadn’t interacted with Nelson and his friends anytime earlier in the night, according to everyone who was interviewed and asked that question.

Kaus told an investigator it was an incident with a bouncer at Blue Bricks that eventually led to an argument between Nelson and Kolstad that ended with punches being thrown. Nelson was able to walk into the bar without being carded and Veroeven had a fake identification card, Kaus said.

Thompson told investigators he and Kolstad had been drinking at South Street when they decided to go to Buffalo Wild Wings for some food. When they found a long line at the restaurant, however, they decided to walk to Kolstad’s house. On the way there, Thompson stopped to talk to Kaus.

Kaus told investigators Kolstad was being nice to Nelson, wishing him luck on his decision to leave the University of Minnesota to play quarterback for Rutgers. The argument started because Nelson mistook Kolstad for a bouncer who had allegedly hit on Verhoeven earlier in the evening.

When Nelson accused Kolstad of trying to hit on his girlfriend, Kolstad told Nelson he was married and wouldn’t do that, Kaus said.

At that point Nelson pushed Kolstad hard, which made Kolstad angry. That’s when Kaus grabbed Kolstad and Thompson grabbed Nelson and took the men in different directions. Kaus and Thompson both said they tried to keep the other two men from taking the argument any further.

“I’m like, ‘Isaac you don’t want to do this,’” Kaus said. “You have a kid, your wife’s three weeks away from having another kid. You don’t need to be doing this kind of stuff. Phil is…he’s intoxicated. I know you hate that he just shoved you like that, but it’s not worth it.”

Kolstad didn’t listen. He got away from Kaus and ran toward Nelson and Thompson.

“He sucker punched him in the back of the head and then Phil like stumbled around like, I mean I’m sure because he got hit in the back of the head,” Kaus said. “Then all of a sudden, right after Kolstad punched Phil in the back of the head, some dude in a red shirt outta nowhere came and just clocked him.”

That man was later identified as Trevor Shelley, 21, of St. Peter, Minn. Shelley is also facing first-and third-degree assault charges in the incident.

Nelson admitted to pushing Kolstad before walking away. He said he was punched in the back of the head seconds later.

“I just remember popping back up and the seeing like I was just I was really out of it and I remember people kinda like holding me up and then somebody in a red shirt hitting the guy to the ground. All of the sudden, yea, I was walking across the street like over by where the cops got me. So I mean it was like a big haze after that and I just remember basically losing my vision for awhile.”

Nelson said he didn’t remember kicking Kolstad.

Veroeven was interviewed later in the day on May 11. She hadn’t talked to Nelson since his arrest. She said Nelson pushed Kolstad, who she had never met before, first but Kolstad started the fight.

“I was standing right next to Philip and the guy goes, ‘I’m getting with your girlfriend tonight’ and that’s what put him over the edge,” she said.

Nelson had a blood-alcohol concentration of .12 when he was tested after his arrest and Veroeven, who was cited for underage drinking, had a BAC of .13. Kolstad’s BAC was .16.

Nelson, who had transferred to Rutgers after two seasons at Minnesota, was dismissed from the program two days after the incident. Kolstad, who had graduated from Minnesota State in 2013, was discharged from rehab and inpatient care in October.

Nienaber writes for The Free Press in Mankato, Minn.