I have just witnessed a sudden death of my old motherboard, and wonder whether a newly added GPU could have caused it.
 
I had the infamous EVGA Z77 FTW (151-IB-E699-KR) running fine for years with i7-3770K (without overclocks) and two EVGA GTX Titans (yes, the original Keplers). A week ago I've replaced the PSU with B-stock EVGA SuperNOVA 1300 G2 (120-G2-1300-RX), and the system kept running fine. Today I received a B-stock EVGA GeForce GTX 1070 Ti FTW2 GAMING (08G-P4-6775-RX), and added it as the primary GPU. More specifically, I've moved the Titans from PCIE slots 1 and 3 to 3 and 6. The 1070 Ti went into the slot 1. Both 6 pin plugs on the motherboard were already connected to the PSU.
 
But as soon as I turned the power on, I saw a tiny flame growing under the newly installed GPU and sensed a strong smell of burning electronics. In a second a flipped the PSU switch (next to the power cable socket) and pulled out the C13 cable for good measure.
 
At first I thought the the newly arrived GPU was defective. However when I pulled it out, I saw that the damage actually happened on the motherboard, close to the SW1 switches that control PCIE slots. 
 


 
Was this just a coincidence and the time has come for the motherboard to die, or could the GPU have caused this somehow? I kind of am hesitant to try this GPU in another motherboard.
 

 
Thanks in advance for your perspectives.
 

Thank you Cool GTX for the IMGUR tip -- I've uploaded the photos with it and linked to the original post. I am actually not a "new" member -- have been registered since 2012 and back in 2017 posted a build log on water-cooling two 1080 Tis with lots of photos. But I did not post in a while, so probably my account got "scaled back"? Anyway, to answer your questions:
 
1) Can't remember hitting/scratching anything while working on the PC, was careful to release the PCIe slot locks and to gently apply pressure when pulling out / reinserting the GPUs.
2) I've just double-checked and can't see any loose bolts or anything that could have shorted the MB.
3) I guess this is a possibility, however I thought I heard the PCIe slot's lock click when inserting the 1070 Ti GPU, so thought it was fully seated.
4) Before I moving/adding the GPUs I turned off the PSU power switch (the one next to the C13 power cord socket).
5) How can I test the new GPU this without risking another MB? Shall I buy a full-width PCIe riser, or could a faulty GPU potentially damage a MB through the riser as well?
6) Yes I was using the power cables that came with the PSU. More specifically, the cables that that have dual connectors (6 pin and 6+2 pin), a single cable per card. However the 1070 Ti in question has dual 8 pin connectors, so I powered it with two of those PSU cables, only using their 8 pin plugs. The SuperNOVA 1300 G2 has 6 PCIe connectors. I've used two cables with single 6 pin plugs for the MB, and then four cables with 6 & 6+2 to power the GPUs. Each Titan was powered with a single dual-plug cable, and 1070 Ti used two of those cables (the 8 pin plugs).
7) Last week I actually already tried a three-GPU configuration on this MB/PSU, with two Kepler Titans and an old GTX 680, all was fine.
 
Thanks for your comments, I would like to investigate #5. Sad to see this MB die; for all its capricious behavior it had a great PCIe slots layout (and looks!). I read it was capable of running up to 4 GPUs (slot 1 at 16x and slots 2,4,6 at 8x via a multiplexer chip) and was thinking of building a water-cooled build in it for compute. I am almost considering buying an identical used MB, just to complete the project (since I still have CPU and RAM from it).
 
Not sure what was the role of the component that got burned on the MB, any ideas?

jll544
The burnt components appear to be related to the PWR_FAN header, and the wires on that connector are chewed up. My guess would be that the 1070's heatsink cut into the +12V wire (pin #2) and shorted it to ground. You might try test fitting the card with the power off to see if there was any contact there.

Agreed, agreed.

 
Glad to hear it.