A manhunt is under way for the perpetrator behind a shooting attack at Rhode Island’s Brown University in the United States that killed two people and wounded nine, eight of them critically.

A shelter-in-place order was in effect early Sunday on the campus of the prestigious Ivy League university and surrounding neighbourhoods in Providence, as law enforcement searched for the assailant.

Here’s what we know so far.

What happened?

On Saturday afternoon, a suspect with a firearm entered Brown’s Barus and Holley building, home to the school of engineering and the physics department, where students were taking exams.

Two people were killed and eight critically injured when the attacker opened fire, with a ninth sustaining injuries from bullet fragments, officials said. The victims are yet to be publicly identified, although the university president, Christina Paxson, has said she was told they were students.

University authorities became aware of the shooting at about 4:05pm local time (21:05 GMT), when emergency responders received a 911 call, Providence Mayor Brett Smiley said.

Seventeen minutes later, the university issued its first emergency update, warning that there was a gunman near the engineering building and advising those present to silence their phones and hide.

Law enforcement swept the building, but the suspect had left the scene.

Who is the shooter?

Officials have released a video of the as-yet unidentified suspect, a male possibly in his 30s and dressed in black.

The Providence deputy police chief, Timothy O’Hara, said the attacker might have worn a mask, but officials were not certain.

Smiley said officials did not believe there was any “specific, ongoing threat” posed by the attacker, who is believed to have fled along a usually busy street of restaurants and coffee shops.

What do we know about the manhunt?

More than 400 law enforcement personnel have been deployed in the hunt, canvassing the local area while a lockdown order remains in place on the campus and surrounding neighbourhoods.

Agents from the Federal Bureau of Investigation and the Bureau of Alcohol, Tobacco, Firearms and Explosives have been drawn into the effort, working alongside local and state police.

Police said investigators had retrieved shell casings from the scene of the shooting and were also looking into why the target was selected as part of the investigation.

What has President Donald Trump said?

The US president told reporters at the White House that he had been briefed on the “terrible” situation.

“All we can do right now is pray for the victims and for those that were very badly hurt,” Trump said.

He published a retraction on his online platform, Truth Social, after erroneously posting that a suspect had been detained, echoing a similar incorrect claim by the university in the early hours after the attack.

What is there to know about the university?

Brown, a member of the prestigious Ivy League of elite private universities in the northeastern US, is one of the oldest universities in the country.

Founded in 1764, it has 11,000 students and a highly selective admissions process, with only about 5 percent of undergraduate admissions accepted in the latest intake.