PITTSBURGH - A gunman who killed a worker and shot several other people at a psychiatric hospital on the University of Pittsburgh campus lived nearby and used two semiautomatic pistols, one of them stolen, as he marched around checking offices possibly in an attempt to find more victims before campus police fatally shot him, authorities said Friday.

John Shick began shooting almost immediately upon entering the Western Psychiatric Institute and Clinic lobby Thursday afternoon, wearing a tan trench coat, T-shirt, jeans and two watches. He also had a fanny pack containing plastic bags with medicines police haven't disclosed and carried a box of ammunition.

Shick, 30, fatally shot one clinic worker and wounded six other people, Pittsburgh major crimes Cmdr. Thomas Stangrecki said at a news conference.

After the initial shootings, Shick went up a stairwell to a second-floor parking area, where he apparently tried to exit but couldn't because he didn't have an electronic card needed to open a secure door. A window on the door was shot but didn't shatter, suggesting Shick tried to shoot his way through.

Police believe Pitt officers, who had trained for a Virginia Tech-style shooting, encountered Shick as he came back down the stairs and into the lobby, perhaps planning to escape through the front door he had entered.

"We practice this," Pitt campus police Chief Tim Delaney said. "A lot of these (law enforcement techniques) came out of Virginia Tech. They engaged in gunfire as soon as they entered the front door."

Police aren't sure how many shots were fired in the brief gun battle, but Delaney said there were so many that smoke hung in the lobby afterward.

No witnesses have reported that Shick said or did anything to explain his motives, and police said they found nothing on him to indicate a reason.

Shick shot seven people, including clinic geriatric therapist Michael Schaab, who was pronounced dead at the scene shortly after the shooting began, the medical examiner's office said. The surviving victims are expected to recover.

Officials at the University of Pittsburgh Medical Center, which is affiliated with the clinic, said they had treated five adults for gunshot wounds. Kathryn Leight, a 64-year-old front lobby receptionist identified by her family as a victim, and a man were listed in serious condition. Two others were still hospitalized, and one had been discharged.

The 292-bed psychiatric clinic is in the city's Oakland neighbourhood, which includes several hospitals and two other universities. That's why Delaney, the Pitt campus police chief, said his officers had trained for a shooting like the one at Virginia Tech, where dozens of people were killed in April 2007, and knew at once they had to stop the shooter at any cost.

Six university police officers responded to the clinic within two minutes of the first emergency call at 1:43 p.m., Delaney said. They were trained to split into two groups of three to outflank the gunman and draw his attention. Police said Shick fired out the front door at the officers as they arrived.

The first three officers returned fire and killed Shick, though police said ballistics tests are still needed to determine which officer fired the fatal shot or shots.

Police are sure that Shick killed Schaab, who was 25, because he was already down from gunfire by the time they arrived, Stangrecki said.

Shick lived in the city's trendy Shadyside neighbourhood, blocks from the clinic. Police hadn't determined if he had a history of criminal or mental health problems, but an online database of state criminal court records revealed no arrests or convictions in Pennsylvania, and a nationwide search of records by The Associated Press turned up only a speeding ticket in Union County, Ore., last April.

Online records suggest Shick once lived near the Carleton College campus in Northfield, Minn., and the college's website shows that a John Shick was a chemistry major and graduated in 2004. They also suggest it was August when Shick moved to Pittsburgh, where he lived in a fairly upscale apartment building that has a mix of tenants, including students and young professionals.

Calls to homes listed in the names of Shick's parents in Green Cove Springs, Fla., and San Jose, Calif., went unanswered Friday.

Stangrecki declined to say specifically how police identified Shick, who was carrying no identification. He said only that Shick's name was confirmed through an unspecified database from a name written on something the gunman possessed or was wearing.

Police said they traced Shick's guns to an unspecified area of Texas and said one had been stolen, but they wouldn't detail their model or calibre.

Schaab, of suburban Edgewood, had worked at the clinic since graduating from Pitt with a psychology degree and was going back to school to get his master's degree in occupational therapy. He had one sibling, a 26-year-old sister, who was fatally shot during a domestic dispute in October 2010; her live-in boyfriend is in prison for voluntary manslaughter.

Schaab had recently gotten engaged, his mother said.

"We were just planning his wedding," Mary Schaab said, sobbing. "March 2013."