Authorities are still searching for answers and for the alleged gunmen in the shooting at Brown University four days ago.

Two students were killed and nine others injured.

Officials have released photos and video showing a person of interest walking near the campus hours before the shooting.

The FBI is offering a $50,000 reward for information leading to an arrest.

There's still concern in Providence about the whereabouts of the shooter.

Providence Mayor Brett Smiley tried to provide reassurance to residents this evening.

The best information we have is that there is no credible, actionable, specific threat that has occurred since Saturday.

And in order to enhance and ensure the safety of our community, we have stepped up law enforcement

efforts throughout the city in a precautionary measure.

For more, I'm joined now by Juliet Kayam.

She's a professor at the Harvard Kennedy School of Government

and former Assistant Secretary at the Department of Homeland Security

in the Obama administration.

Juliet, thank you for joining us.

Thanks for having me.

So you heard officials there asking for the public's help, releasing these images,

from your experience, how helpful could this be, these images in particular, and what do

you make of the fact that they still have not identified or found this suspect?

Yes.

I mean, in some ways, this isn't really a manhunt because they don't know who the man is. I mean, manhunt is generally you have an image or even a name and you're going after them, you know, talking to family and friends. It is remarkable and unusual in this day and age with that many cameras, with students with phones that they cannot seem to get a great picture of his face.

He was, of course, masked through in some of these pictures or in all the pictures.

So this will be helpful for the sole purpose of convincing someone who recognizes him,

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