silverado won't start hear two clicks now get nothing

So, my husband changes the oil filter like he always does only the truck is
parked on an incline to drain completely.  We also just had the brake line
replaced on the driver side.  All of a sudden he went to turn the key - heard
two clicks and then Nothing.  I mean, NOTHING.  we checked fuses,
cleaned battery terminal, and tried to jump it.  still nothing.  While i was
playing with the key - I could get the beeping sound when the key was
about 3/4 the way in, but not engaged enough to turn the key.  Weird.

Wondering if the knock sensor could be a culprit?  or if there are starter
wires near the brake line that could have been tampered? (starter is on the
other side from replaced line).  Would love some Feedback, y'all!