Warning!
~This thread may contain spoiler~
So, did Mason killed President John F. Kennedy?
If you've seen the last part of the mission when you tried to kill Dragovich.
You: You tried to make me kill my own president!
Dragovich: Tried?
Oh look! Mason is in the crowd just before Kennedy's assassination.
NUMBERS!
0
11
24
11
1
7
19
20
10
14
2
3
19
0
8
11
22
21
5
17
It is implied. Most likely he does, but it isn't certain