[Update Below] Yesterday, NYPD Commissioner Ray Kelly revealed that the two brothers accused bombing the Boston Marathon had planned to travel to NYC to go party after their photos had been released to the world. But officials tell NBC that there may have been more to it than that: their source says Dzhokhar Tsarnaev subsequently told investigators that he and his brother discussed the idea of exploding the rest of their bombs in Times Square.

The brothers did indeed have more explosives on them when police caught up to them Thursday night. However, officials cautioned to NBC that the idea was "aspirational" and not developed. Either way, immediately after NBC's report was released, a press conference with Kelly was announced for 1:30 p.m. at City Hall. You can watch it live below, and we'll update this post once that's happened.

Update: Mayor Bloomberg and Commissioner Kelly held a joint press conference this afternoon to confirm reports that the alleged Boston bombers had been planning to attack Times Square. "Last night, we were informed by the FBI that surviving Boston attacker revealed that New York City was next on their list of targets," Bloomberg said. "The surviving attacker told the FBI that he and his brother intended to drive to NYC and detonate additional explosives in Times Square."

Kelly expanded on that plan a bit, saying that they "spontaneously" decided on Times Square as a target on Thursday evening, after they had carjacked a man near Watertown. "That plan fell apart when they realized the vehicle they hijacked was low on gas," Kelly said. "They ordered the driver to stop at a nearby gas station. The driver was able to escape and call the police. That led to the shootout in Watertown."

Kelly said Tsarnaev brothers were carrying six improvised explosive devices on them: one was a pressure cooker bomb (similar to the two they detonated at the marathon), and the other five were pipe bombs. They didn't have any specific details about where in Times Square they were planning to target, nor when.

Dzhokhar Tsarnaev is known to have visited Times Square at least two times last year, in April and November 2012; officials don't know whether those visits were related in any way to the "spontaneous" decision to bomb Times Square.

During the first interview with Tsarnaev, which occurred between Saturday night and Sunday morning, he told officials the brothers were planning to go to NYC Thursday night to party; that story changed in the second interview, which occurred between Sunday night and Monday morning. Bloomberg reiterated several times that the NYPD never interrogated Tsarnaev—the FBI and local Boston police departments provided the information to them—but Kelly added: "To the best of my knowledge, [Tsarnaev] is speaking. He was more lucid in the second interview, more expansive at giving detail. The first interview was a relatively short time after he went into hospital."

Ray Kelly said it's "unknown" whether NYPD's counter-terrorism measures would have been able to thwart the Boston bombers' plans, but he said there was no evidence that NYC is a target of another attack stemming from the Boston bombings. Bloomberg was a bit testier when he was questioned about what NYC has done since the bombings, and what it might have done if this plan came to fruition: "We don't make light of anything. We have to assume the worst, and deploy our resources to make sure it doesn't happen....Whenever we get information we take it seriously, no matter how far fetched it may be, or no matter whether we think it may accurate."

He added at the end that he feels safe going out tonight: "It's a dangerous world, but you're probably safer here than everywhere else," he said."We've spared no expense, and we've never let our guard down in the last [11 1/2 years]." Bloomberg was also asked at one point whether stop-and-frisk could have helped catch a terrorist suspect: "Stop and frisk is designed to get guns out of hands in the street. The likelihood of finding a terrorist and stoping and frisking isn't great."