In NY and PA,
while it is a violation to tresspass on unposted land,
its not a criminal violation and all wardens can do is tell the tresspasser to leave,
dont think one can be fined/charged with tresspassing on unposted land, unless a criminal violation also occurs while tresspassing,
if one is advised of no tresspassing, either through posting signs, or direct notification, then the tresspasser can be charged witha higher degree of tresspassing,

law, on mercy kills?
havent looked into that, i was under the impression while hunting,
after tracking one is allowed to take a shot as a mercy kill, that would be on an animal one initially shot,
how that applies when final shot is placed after season date i dont know. probably npt legal,
pure speculation here,

as a property owner they should inform the person no hunting allowed,
and to enforce that they should get local officials involved,
local cops tend not to do much on general tresspassing,
but if game violations occurred game wardens would probably be more interested.