LE isn't going to say we have new leads from 'a witness' with previously withheld information. They do not want to release any detail of where the new lead(s) came from, just that they have it from previously withheld information. This is for the integrity of the investigation and protection of the witness . Klein, however, can say "a witness, with direct knowledge, not hearsay, with previously withheld information" (not direct quotes) all he wants. What he says is not held to the same standards as that of LE.
Klein is almost playing bad cop in this while LE plays good cop. Klein issues veiled threats, not LE.
It sounds to me that Klein got someone to talk and then that person also talked to LE and disclosed the previously withheld information. It is likely someone LE talked to before and now they are nervous about not telling what they knew during earlier interviews. Remember Klein would not release his last statement until LE had it and then it was requested that the statement release be delayed. At least Klein stated on his fb page that it was requested that the release be delayed for 24-48 hours. We do not know who requested that but, if it was LE it was because they were talking to the witness.
Klein said he was now vetting the information but, if LE has the info, you can believe they are vetting it too.
Something is happening and Klein got it started.
The new witness(es) can not be IR. Unless Klein is lying when he says that IR didn't talk to him, it is impossible for Klein to have gotten any info from IR. So, these new witnesses are other than the 4 POIs.
How can you get information that was previously withheld in any form other than a witness? My mind is blank on what other way(s) one could possibly get information previously withheld from LE.