It's possible, but pretty coincidental...
...If you received the two emails within the same 24 hour period, there's a pretty good chance it was the same person. I don't know AOL, but I know with a lot of ISP's, you get a "lease" of the IP for a 24 hour period (can vary, but that is the average). Generally, that address is "renewed" if online after the 24 hours, so it's even possible after the 24 hours.
However, if the user logs off before the end of the 24 hours, and then back on after the 24 hours, you get a new "lease" for 24 hours from that point-- it may or may not be the same IP.
It sounds like you suspect it was the same person even from the emails themselves (enough to compare the headers)... it probably was.