Collins translates 'even' as 甚至, as can be substantiated on ZDIC.net. But what semantic notions underlie 甚, 至 with "even"?
ABC Chinese–English Comprehensive Dictionary (2003). I can't access the "slightly revised through July 2005" ed.
甚 = extent
至 = to
甚至 = to the extent of (literal meaning)
(甚至)殺人(也)做得出來 = (to the extent that) he will do killing (too) = (even) killing (too) he would do
The extended meaning of "even" in 甚至 is implied from the implied 也(too) in the [甚至 ... 也] structure
Note: the literal meaning of 甚至 (to the extent of) is as commonly used as "even". e.g. 甚至不吃不喝 (to the extent of not eating or drinking)