Good evening everyone, I'm Allison Kamerata. Welcome to CNN Tonight. The Coast Guard says

a catastrophic implosion killed the five passengers on board that submersible that was headed

to the wreck of the Titanic. We're learning tonight that the Navy picked up the sound of

an implosion on an underwater listening system on Sunday, just hours after the sub-loss

communications. So why did the search go on for four more days? We've got a live report

from the Pentagon coming up. We'll break down everything we know tonight about the victims

on the ill-fated journey and what went wrong. Plus, you just heard Christian Amin Por's

exclusive interview with former President Obama, and tonight we've got reaction to what

he says about the indictments of Donald Trump. We'll also examine what he says about

his former Vice President, Joe Biden. So stick around for that. But let's begin with

news of the Titanic submersible. CNN's Jason Carroll is live in Boston where some of the

Coast Guard's searchers were based and Orrin Lieberman is at the Pentagon for us. Okay,

so Orrin, you're getting new information about this top secret at the time, Navy system

that detected this implosion very soon after the sub-loss communications. So what do we

know tonight? That's right. A senior Navy official tells us that the Navy picked up on

a sound or acoustic signature that was likely or could have been an implosion or an explosion

at about the time the Titans of Bursable went missing and at about the location where it

went missing. According to that senior Navy official, the Navy then immediately passed

that information onto the incident commander and it was then used to refine and narrow down

the search area, an incredibly wide area as we've learned over the last couple of days.

So why didn't it end the search immediately? And this is a crucial question, especially

when it was picked up on Sunday. That's because the Navy official says the sound itself was

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