what killed Reese?

He actually got shot by the T-800's machine gun rifle whatever that was. The pants killed him.

Could have been just him succumbing to his multiple wounds. The smack to the head from the terminator might have given him brain hemorrhage but he stayed alive long enough to put the bomb in the terminator and roll away. He was pretty close to it too when it went off so the concussion from the explosion could have killed him.

VD

Could have been the smelly pants. I think more likely a broken neck. Nasty forward roll after dispersing the last pipe bomb. 💥

Definitely hobo pants

Same reason Vader’s wife dies after giving birth. He lost the will to live.

1) He got shot by the terminator (NOT T800 or T-800 - unless you can show me a portion of this movie where 'T-800' is mentioned, said or uttered, you have no right to use that term here)

2) He was near an explosion around the time he got shot

3) He got further injured when the car turned over (he wasn't wearing a seatbelt and there was no airbag)

4) He strained himself running around and jumping into a garbage can after putting a bomb into the big hole in the truck (looked a bit weird for some kind of tailpipe, so I don't know what it was)

5) He inhaled a lot of smoke in his injured condition

6) He further strained himself when he should've been resting, when running away from the stop-motion version of the terminator

7) He was nagged by a fema-fascist hag that only sees him as a 'soldier', not a human being

8) His stress levels kept rising, as the terminator came closer, and he realized he had to face it head-on in close combat

9) He had burdened himself with so much - the stakes were extremely high - and now he had to protect someone who is in much better health but doesn't help even herself, let alone realize to run (stress caused by stupidity and stubbornness of Sarah)

10) The terminator punches him, causing more injury, fear and stress, and who knows what other damaging feelings

11) Another explosion on top of all that with sharp metal bits hitting his already badly injured body was just too much

What's so hard to understand about all thaT?

His love for Sarah Connor.