So, 2 of the letters must be from science profs. but this last one, can it be from anyone, as in LOR from work or volunteering, or just any other prof.?
The first post of this thread says that it must be from any other prof. but on the website it says it can be from anyone...
http://tulane.edu/som/admissions/admissions-process.cfm
"Tulane's letter of recommendation requirement is as follows, a committee letter, letter of recommendation packet, or three letters of recommendation, two must be from professors of science, and the third letter can be from
anyone of your choice."
VS.
"
You should submit a composite evaluation prepared by the faculty committee of your undergraduate institution. If your school does not provide such a composite, then submit three individual, separate letters of evaluation, two of which should be from professors of science under whom you have studied and the third from a professor of your choice."
Yeah, I noticed that discrepancy too (anyone vs any professor of your choice for the 3rd letter). I think you can send your strongest letter from anyone for the 3rd letter. You can just cite the website if they questioned your 3rd letter. I had my research supervisor as my 3rd letter.
Also about additional letters. I was trying to figure out a way to send them additional letters. I called them and a lady said if I send in a letter packet (listed as one single letter entry on AMCAS) and inside contains 6 letters (more than 3 letters), it will be accepted. However, if I send in letters individually (separate entries on AMCAS), then I can only send in a maximum of 3 individual letters. I took this as maybe they don't want to process through adding more than 3 letters separately to your file. But just in case they would pick only 3 letters out of the 6 letters in the single letter packet (didn't ask her about this), I explicitly wrote out whose letters I want them to use to satisfy the required letters in one of the 2ndary app responses.
So main point of the story is this: You can send
1) A single letter packet which inside contains more than 3 individual letters of rec
OR
2) maximam of 3 individual letters of rec
Method (1) is a bit risky, so it's best to state somewhere in your 2nd app that you want them to use what letters for the 3 required. Or just be safe and choose option (2).
Also it takes time for you to send a letter packet now to AMCAS and for them to process it. Although it took only 2 days after sending the letters via Interfolio for AMCAS to mark them as received, I don't know if it'll be that quick for you. So think if it's worth the wait for you.
Also notice the webiste LOR instruction is as follows:
"Tulane's letter of recommendation requirement is as follows, a committee letter,
letter of recommendation packet,
or three letters of recommendation, two must be from professors of science, and the third letter can be from anyoneof your choice."
Hoping for good news soon! 
