US authorities brought James Currie back from Thailand Thursday night to face charges.
Investigators say the last time 7-month-old Mason Saldana was seen alive was Saturday afternoon when Currie was seen on video entering his apartment.
That was 20 minutes after the baby boy's mother handed off her son.
Police say the mother called 911 Monday when she saw the body of a baby had been found.
The child was discovered on an embankment of the East River under the Brooklyn Bridge on Sunday wearing only a diaper.
Currie was later spotted walking near South Street Seaport roughly an hour before his son was located in the river by tourists. The next day, he hopped on a flight to Thailand.
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