Gunman kills one, injures three on Seattle campus

A gunman stormed a college in the northwestern US city of Seattle and shot four people, one of them fatally, before he was brought down by a student security guard wielding only pepper spray.

In what the city mayor denounced as the latest example of America's "epidemic of gun violence," the shooter opened fire on campus with a shotgun and was only halted after he stopped to re-load.

The assault came just two weeks after a disturbed young man opened fire at a California university and killed six people.

Those wounded at Seattle Pacific University were being treated in hospital. The dead victim was a 20-year-old man who was shot in the upper body and died on his way to hospital.

A young woman in her 20s was also shot in the upper body and was in a "serious condition" and undergoing surgery. Two more young men were hurt, one of them receiving pellet wounds to the neck.

Seattle Assistant Police Chief Paul McDonagh said the gunman was a 26-year-old white man. Seattle Pacific is a small a private Christian university with 4,000 students.

The attacker was armed with a shotgun and a knife. And, in what police said was a sign that he have planned to kill more people, he also carried several additional rounds of ammunition.

"But for the great response by the people at Seattle Pacific University, this incident might have been much more tragic," McDonagh said.

Police described a "dynamic" crime scene, with investigators still processing the area due to the many witnesses and "a lot" of evidence.

They plan to release the suspect's name once he has been booked into jail and charged.

The gunman opened fire in a lobby of a science building on the campus.

He was "subdued after being pepper-sprayed by a student security guard," a police statement said. Initial reports suggested there were two gunman, but police said that proved false.

Mayor Ed Murray expressed outrage that his city had fallen victim once more to the gun violence plaguing the United States.

"Today should have been a day of celebration at the end of the school year. Instead it's a day of tragedy and of loss," he told reporters.

"Once again, the epidemic of gun violence has come to Seattle, the epidemic of gun violence that's haunting this nation."