How did Hagrid and Dumbledore know the Potters had been killed?

In Harry Potter and the Sorcerer's Stone it says:

"No problems, were there?" [Dumbledore asked]

"No, sir - house was almost destroyed, but I got him out all right before the Muggles started swarmin' around. He fell asleep as we was flyin' over Bristol." [Hagrid said]

Dumbledore and Professor McGonagall bent forward over the bundle of blankets. Inside, just visible, was a baby boy, fast asleep. Under a tuft of jet-black hair over his forehead they could see a curiously shaped cut, like a bolt of lightning.

Sorcerer's Stone - page 11 - US Hardcover

How did Dumbledore - who I'm guessing dispatched Hagrid to go and survey the scene at the Potters' home in Godric's Hollow - know the Potters had been killed? Neither Dumbledore nor Hagrid were the Potters' Secret Keeper for the Fidelius Charm. How was Dumbledore alerted instantaneously that James and Lily had been killed, in order to be able to send Hagrid to the scene quickly enough that he was able to rescue baby Harry before the Muggles were alerted to the situation (which, to be honest, seems a bit unlikely if there was some kind of explosion, which it seems there was seeing as the house was "almost destroyed"). Heck, if the house next door to mine suddenly blew up, it would take me less than 10 seconds to get out onto my porch for a look-see!

How can these events logistically make sense?

ETA: Information on the Fidelius Charm.

When a Secret-Keeper dies, their secret dies with them, or, to put it another way, the status of their secret will remain as it was at the moment of their death. Everybody in whom they confided will continue to know the hidden information, but nobody else.

Just in case you have forgotten exactly how the Fidelius Charm works, it is

"an immensely complex spell involving the magical concealment of a secret inside a single, living soul. The information is hidden inside the chosen person, or Secret-Keeper, and is henceforth impossible to find - unless, of course, the Secret-Keeper chooses to divulge it" (Harry Potter and the Prisoner of Azkaban)

In other words, a secret (eg, the location of a family in hiding, like the Potters) is enchanted so that it is protected by a single Keeper (in our example, Peter Pettigrew, a.k.a. Wormtail). Thenceforth nobody else – not even the subjects of the secret themselves – can divulge the secret. Even if one of the Potters had been captured, force fed Veritaserum or placed under the Imperius Curse, they would not have been able to give away the whereabouts of the other two. The only people who ever knew their precise location were those whom Wormtail had told directly, but none of them would have been able to pass on the information.

J.K. Rowling's Website - The Fidelius Charm

I note that there is no canon evidence that Peter Pettigrew told anyone of the Potters' whereabouts except for Voldemort, and Voldemort, following the confrontation, wasn't exactly in the position to be playing Tellyfone with Dumbledore!