UN seeks immunity for UNRWA employees complicit in Oct. 7 massacre - Channel 12 report

[Eko]

55. That is what Israel claimed orally to UNRWA that there were Hamas operatives working at UNRWA.

UNRWA fired them with only the claim from Israel.

"On 26 January, in response to allegations received orally from Israeli officials regarding the alleged involvement of 12 UNRWA staff in the 7 October attack against Israel, and upon ascertaining that the individuals were indeed UNRWA staff members, the UNRWA Commissioner-General decided to immediately terminate the appointments of these staff “in the interest of the Agency,” in accordance with applicable staff regulations, in order to protect its ability to deliver humanitarian assistance."

https://www.unrwa.org/unrwa-claims-versus-facts-february-2024
UNRWA then conducted an investigation and fired 9 employees that may have been involved.

"“In one case, no evidence was obtained by OIOS to support the allegations of the staff member’s involvement, while in nine other cases, the evidence obtained by OIOS was insufficient to support the staff members’ involvement,” he said."
"“I have decided that in the case of these remaining nine staff members, they cannot work for UNRWA. All contracts of these staff members will be terminated in the interest of the Agency,” he said."

https://news.un.org/en/story/2024/08/1152841
There is more at the link.
I think that addresses your first claim that it was a known fact, it was not.
To address your question "Can you prove UNRWA has completely purged all Hamas operatives? " of course not. Can you prove the USMC has purged all white supremacists? Of course not. Does that mean that the USMC is providing cover for terrorists? Of course not.