Kerboom...Yikes!

Half awake at 4 a.m. there was a loud explosion, and then a car alarm went off. I tentatively looked around but there was no one. The man over the road, an off-duty police officer, was up looking at the car. But there seemed to be little or no damage.
I went back to bed and was awakened 45 minutes later. Two young cops.
"Did you hear an explosion?"
"Yes I did."
"Well it was your letter box, and there 's a piece of it there."
Curiouser and curiouser, the piece had flown about 30 or so feet...I mean 10 metres ...and landed surprisingly just outside the front door. Still no one to be seen.
Dear Tilly didn't make a noise. I am now awake! Bugger!