A man squeezed through the sunroof of a Jaguar (search) early Tuesday and opened fire with an assault rifle on another moving vehicle, killing three men and critically wounding a fourth, police said.

Authorities were searching for the gunman and two others who may have been riding in the light-colored Jaguar with fancy wheels, police said.

University Park police Capt. Robert Brown said the shooting may have stemmed from a scuffle at a bar earlier in the evening. He said the shooter apparently waited for the other party to leave the bar, and then followed in the Jaguar. The shooting occurred around 2 a.m. on a highway frontage road near the Southern Methodist University (search) campus, police said.

"Apparently, there was a dispute on the dance floor in which somebody got hit or punched," said Mike Turiace, who was tending bar at Jack's Pub & Volley Ball club Monday night. "The guy just got angry and decided to pursue it."

A police officer waiting at a traffic light at the intersection witnessed the shootings and stopped to help when the gunned-down car crashed, Dallas (search) police Sgt. Gil Cerda said. Police policy prohibited the officer from pursuing the fleeing Jaguar because he already had a prisoner from an unrelated case in his back seat.

Investigators on Tuesday impounded a Jaguar they believe was involved, University Park police Capt. E.L. Holman said. "I'm sure that it was found abandoned because there were no arrests made," he said.

Turiace and others said Jack's Pub is normally a safe, friendly place that hosts festivals and volleyball matches and attracts a college crowd from SMU.

But the clientele shifts a bit on Monday nights, when the business advertises $2 drinks, a packed dance floor thumping with two DJs and a time so good "You won't believe it's not Saturday," according to the pub's Web site.

"There's arguments, there's altercations, people that need to be escorted out, just like any other bar," the bartender said. "It's not a trouble spot, it's not a hot spot by any means."

Turiace said the fight didn't cause a big stir in the crowded pub, but its policy is to escort instigators outside after a fight.

"It wasn't anything out of the ordinary that would lead to this. I guess certain people have it in their minds that this is their type of proper justice," Turiace said. "That really scares me."

University Park, a city of only 4.5 square miles, has an extremely low crime rate and doesn't see many homicides, Brown said.

"This is new to us, but we're capable of investigating it," he said, noting that Dallas police are assisting.

"I don't think it's going to be a hard case," Brown said. "Obviously, when you have people who are at a location such as a pub, hopefully, we can find witnesses who were at the location who can help us solve this crime."

Killed were Eddie Pech, 36; and cousins Bernardo Andrade, 21; and Favio Andrade, 19, police said. Osvaldo Juarez, a juvenile whose age was not released, was listed in "very critical" condition.