McKINNEY, Texas -- A 29-year-old man towed a trailer full of explosives into a suburban Dallas police station's parking lot Tuesday, then set fire to his pickup truck and began shooting at the building in an apparent attempt to lure people outside to kill them, authorities said.

Patrick Gray Sharp died after a shootout with officers, but it's unclear whether he was killed by an officer's bullet or one of his own, McKinney police chief Doug Kowalski said.

No one else was hurt during the Tuesday morning clash.

Sharp may have intended to lure people from the police station so that he could shoot at them from a field across the street where he had taken position, Kowalski said. He also may have intended to kill them by blowing up the trailer, he said.

The fire set off ammunition in the truck but failed to ignite the trailer, which was filled with wood chips, ammonia nitrate, gasoline and road flares, Kowalski said.

Patrick Gray Sharp is shown this undated hand out photo released by the Texas Department of Public Safety, Tuesday, Aug. 17, 2010. McKinney police have identified Sharp as the man that opened fire on officers outside their police station in McKinney. (AP Photo/Texas Department of Public Safety)

Investigators found an assault rifle, a shotgun and a handgun on Sharp. Kowalski said Sharp fired at least 100 rounds at the police station and that he counted at least 23 bullet strikes on the building.

Sharp was found dead after police fired an unknown number of rounds while pursuing him in a line of trees where Sharp had taken cover and into an open field near Collin College, the chief said.

It wasn't clear how Sharp died, but Kowalski said a witness indicated he might have shot himself. The chief said investigators haven't determined why Sharp initiated the attack in the suburb of roughly 127,000 people about 30 miles north of Dallas.

"He had a plan. He was activating his plan. He was heavily armed," Kowalski said. "He looked like he knew what he wanted to do. What we don't know is why he wanted to do it."

Sharp's roommate, Eric McClellan, said that he was on vacation outside of Texas when he received calls from state troopers and his stepfather telling him what happened. He said he was "still in shock," and that there was nothing about Sharp that would lead him to believe he would try to attack police.

"He was fine and dandy when I left Texas two days ago, and, all of a sudden, I get a phone call," McClellan said. "There's nothing I can say. He was a great guy, a good friend."

McClellan said he was questioned about Sharp by police and couldn't provide them with much information.

He said he and Sharp kept guns in their residence because they like sports shooting.

"We're Texans," he said. "We have the right to bear arms."

McClellan said he was doing contract work for building wire manufacturer Encore Wire Corp. six years ago when he met Sharp, who was an employee of the company. They had been roommates for four years, he said.

Collin County records show that Sharp and McClellan are co-owners of the manufactured home they shared near Anna, a town about 15 miles north of McKinney.

Matt Payne, who witnessed some of the clash, said he was on his way to work with his wife and 10-year-old son when they heard "this popping sound" while they waited at a red light near the police station. They drove in front of the station and saw the truck engulfed in flames before looking across the street and seeing a man in an open field in an olive-colored flak jacket and carrying what looked like a military-style rifle.

A campus police vehicle drove around a building and the man turned his weapon toward the officer's car before gunfire broke out, Payne said.

"He was not hidden at all," Payne said. "It was obvious that he intended to go and hurt people and wasn't real concerned about whether he made it or not."

Ed Leathers, Collin College's police chief, said the gunman shot several times at a campus officer's patrol car. One of the bullets penetrated the back of the vehicle and would have struck the officer if it hadn't been stopped by a metal plate behind the back seat, part of the safety divider that separates officers from those in the back, he said.

"He came one inch from being killed possibly," Leathers said. "The bullet went straight for his back and lodged in that plate."

Leathers said the officer, a veteran of more than 20 years of police work, was on a routine patrol when he came across the gunman. He said there was a shotgun in the vehicle, but the officer never got a chance to use it.

Several other campus officers were then dispatched to the scene, but none discharged their weapons, he said.

Leathers said bullets from the shootout also penetrated a metal building on campus. School employees were in the building, which is mainly used for records, but none were hurt, he said.

Leathers said the incident was the first time in the 10 years his department has existed that there has been shooting on or near the campus.

Texas Department of Public Safety spokesman Tom Vinger said Texas Rangers, highway patrol and DPS aircraft were on the scene or headed to the area. Vinger could provide no further details.

The Collin County Community College District sent an e-mail alert to college staff and students shortly after 9:30 a.m. Tuesday warning that shots had been fired and that the central campus in McKinney was closed.

The e-mail said: "Shots fired. Campus on lockdown. Cops on the scene. Details to follow."