Salt Lake City police responding to a call about a shooting inside a local truck stop Wednesday found Roger Malcolm calmly sitting down, a handgun on a chair next to him and a security guard lying at his feet in a pool of blood.

"This is just cold-blooded," said John Walker, a trucker from Denver who watched the incident unfold from the parking lot. "The guy just sat down and watched him bleed. That's crazy."

Malcolm, 51, a regular at Sapp Brothers, 1953 W. California Ave, was hollering at a clerk just before the 3 p.m. shooting occurred, said Salt Lake City Police Lt. LaMar Ewell. He had wanted to purchase a package of gum and felt he had been waiting too long for service, Ewell said.

Hearing the commotion, 31-year-old security guard Verne Walter Jenkins asked Malcolm to leave. Malcolm continued arguing, according to police, so Jenkins attempted to escort him out of the truck stop that houses a Burger King, gas station, 24-hour diner and showers and parking facilities for big rig drivers.

Police said Malcolm then pulled out a handgun and shot Jenkins in the neck. Police tried to revive Jenkins, who died at the scene.

Police took the waiting Malcolm into custody when they arrived, said Salt Lake police spokesman Jared Wihongi. After being arrested, Malcolm became defiant and uncooperative. He has been booked into the Salt Lake County Jail for investigation of aggravated murder.

Police said they learned Malcolm visited the truck stop often and was known to be foul-mouthed and belligerent, Ewell said. Malcolm has lived near 1600 South and 1300 West since at least 1994.

About an hour after the shooting, Malcolm was placed in the rear of a squad car parked just to the east of the business. Every few minutes, officers opened the door of the car to talk with him. He could be heard yelling obscenities from dozens of yards away.

Fifteen minutes later, officers moved Malcolm to a second squad car, which then drove off.

Several witnesses to the deadly shooting were kept inside the restaurant for more than an hour. Others were taken to the Salt Lake City police headquarters for further questioning, said Wihongi.

Sapp Brothers was closed for the evening.

Concerned citizens milled about throughout the afternoon, trying to learn what had happened.

"I come here all the time," said Dave Kilgrow, a Salt Lake resident. "They have a security guard here all the time. They usually keep a pretty tight ship."

Kilgrow said the security guards were never armed. Private security guards are common at truck stops nationwide, he said.