IMO, the fact that two projectiles were used shows that theact was carried out by two kids Fing around. Considering the time of year, I'd say this is a stupid Halloween prank. I also think the rock was thrown and not launched from a device. Looks like the rock is of a size that could be whipped really hard.

Z-man, a suggestion.

http://www.windowtinting.net/residential.html

I have it on all my windows and it works. My son was horsing aroud in his room and fell into his window. Instead of going through he cracked it and it was intact.

There is a house in town here that was struck by a solid object in Hurricane Wilma the window is smashed and dented in but still in tact.