Wow....sounds like you dealt with a wise bunch of people there!

Sprayed water into the intake to stop the engine!?! I'd have done the same to their fire truck motor! They could have just hosed it off to get the fire out then stopped the motor. What a waste...engine is probably done for from trying to compress water, not to mention water flooding through the hot turbo...
I bet this was caused by the resistor for the blower under the brake booster, probably filled with leaves and debris, thus caught fire. Looks like it started in that vicinity.
Too bad

Looks like it was a nice car still. Most you can do now is probably just part out what still works. The transmission should still be ok, as well as other drive components and body parts other than the hood/front.
This is why I always keep extinguishers in all my cars....
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'15 GLK250 Bluetec 118k - mine - (OC-123,800)
'17 Metris(VITO!) - 37k - wifes (OC-41k)
'09 Sprinter 3500 Winnebago View - 62k (OC - 67k)
'13 ML350 Bluetec - 95k - dad's (OC-98k)
'01 SL500 - 103k(km) - dad's (OC-110,000km)
'16 E400 4matic Sedan - 148k - Brothers (OC-155k)