Not to side with the police officer, but this might explain his concern.

From Sunday's Free Press: John Carlisle: Detroit firefighters do duty amid chaos
It was the middle of the night. The house was being swallowed by flames. Firefighters were rushing inside.

And out of nowhere, a man appeared and stood in front of the burning house on Detroit’s east side, staring at the fire like he was enthralled. Was he the one who started it?

Firefighters say arsonists often return to the scene of their handiwork to admire it. Firefighters have taken photos of the crowds gathered at various blazes, and they later notice that some guy will be at each of them, gazing out from the crowd with that same entranced stare.

“Usually those guys like to watch their work,” said 54-year-old Lt. Tom Holt of Engine Company 58, the first of three engines to arrive at the scene on that Wednesday night in August. “It’s a disease, like kleptomania, alcoholism, whatever. They’re pyromaniacs.”

As if firefighters in this failed city don’t already face enough indignities, on nights like this they sometimes have to stand side by side with the person who might have started the fire they’re risking their lives to extinguish.
So maybe they should be encouraging more photography to increase the chance of identifying arsonists.