The gunman who killed three people at the University of Nevada on Wednesday, December 6, was a 67-year-old professor who had been rejected for a job at the college.

His failed job application was reported by 8 News Now, with sources telling the site that he may also have had connections to a person who works on campus.

The three people who died have not been named. A fourth victim was shot but is in stable condition, said Sheriff Kevin McMahill, speaking at a press conference on Wednesday night.

He said four additional people are in hospital after suffering panic attacks, and two officers were treated for minor injuries.

McMahill praised the 'heroic' officer who stopped the gunman but said they were unable to specify what weapon was used.

US President Joe Biden said the shooting, days after six were shot dead in Austin and San Antonio, was 'not normal, and we can never let it become normal.'

Biden said he was saddened that the university 'became the latest college campus to be terrorized by a horrific act of gun violence.'

He thanked the first responders and said it showed that more must be done to end the epidemic of gun violence.

'This year alone, our nation has experienced more than 600 mass shootings, and approximately 40,000 deaths due to gun violence. This is not normal, and we can never let it become normal,' he said, in a statement issued by the White House.

'For all the action we have taken since I’ve been President, the epidemic of gun violence we face demands that we do even more.

'But we cannot do more without Congress. Republican lawmakers must join with Democrats in Congress to ban assault weapons and high-capacity magazines, pass a national red flag law, enact universal background checks, require the safe storage of guns, and advance other commonsense measures that will help stem the tide of gun violence.

'And together, we must do more to prevent more families, and more communities like Austin, San Antonio, and Las Vegas, from being ripped apart by gun violence.'

Adam Garcia, the director of university police services, said the first 911 call came in at 11:45am.

'Officers immediately responded and engaged the suspect,' said Garcia. He said the suspect was shot and killed by the officers.

'The entire Nevada system of higher education and campuses are closed, out of an abundance of caution. There is no threat to other campuses, but they are closed out of an abundance of caution.'

A huge police presence including tactical teams were seen scrambling to the college after an alert was issued to students, warning them to 'RUN-HIDE-FIGHT.'

In response to the campus shootings, the Federal Aviation Administration issued a ground stop for all flights coming into Harry Reid International Airport.

Less than an hour after the alert was released, the Las Vegas Metropolitan Police Department announced the suspect was deceased. The force said the investigation is ongoing.

Officials said 'multiple victims' had been targeted in the attack.