Hook - THEN info dump

I'm reading chapter one of a Jeffery Deaver novel.

A security guard at a music school hears a scream. Instead of investigating the noise by himself, he looks for assistance. On the sidewalk he finds 2 young female police officers on their morning watch. The police women normally deal with shoplifters or traffic offences and aren't experienced with murder victims.

Deaver wants the reader to know how the 2 police officers came to be there. And I see how the tension is raised if the reader worries about their lack of experience, but he avoids opening the section with an info dump. He starts with the anxious guard talking to the police. Then he shows how they got to be standing together discussing a suspicious noise.

'You're sure it was screaming?'
   'Yeah . . . . No,' the security guard said. 'Maybe not 
screaming, you know. Shouting. Upset. For just a second or two.
Then it stopped.'
   Officer Diane Franciscovich, a portable working out of the
Twentieth Precinct, continued, 'Anybody else hear anything?'
   The heavy guard, breathing hard, glanced at the tall brunette
policewoman, shook his head and flexed and opened his huge 
hands. He wiped his dark palms on his blue slacks.
   'Call for backup?' asked Nancy Ausonio, another young patrol
officer, shorter than her partner, blonde.
   Franciscovich didn't think so, though she wasn't sure. Portables
walking the beat in this part of the Upper West Side dealt mostly
with traffic accidents, shoplifting and car theft (as well as holding
the hands of distraught muggees). This was a first for them - the
two women officers, on their Saturday morning watch, had been
spotted on the sidewalk and motioned urgently inside by the guard
to help check out the screaming. Well, upset shouting.

   

I can see how the info about the officers' background and the fact the guard has asked them for assistance would be dull writing without the tense exchange planted before it.

I hadn't fully realised until now that the device of 'first the hook, then the info dump' can used continually. Good writers always make sure the reader will be ready to absorb the info dump - even a small info dump.