[JamesVI]

At this point I would say no,

Document and hand off to HR. If the colleague comes to you and asks if you reported to HR then you can be honest and say you did because you were concerned for their well-being.

Talking to them doesn't really help them. It forces them to decide if they want to endorse you talking to HR or to claim it was "no big deal". HR is (supposed to be) trained to deal with this kind of situation and should be better equipped to decide how to proceed.

[anydden]

But that would be too much right ? I don’t have any proof that it was harassment , could be just normal drinks I also offered her one , but this guy was certainly trying to touch her shoulder hold her hand , and call out her name multiple times

[JamesVI]

The situation you witnessed and heard about made you sufficiently uncomfortable to create a throw-away account to ask HN for advice. That level of discomfort is sufficient to report it to HR. For all you know there have been other complaints made in the past and this incident will complete a picture of a pattern of troubling behavior.

It isn't your responsibility to gather proof or to make a career-impacting decision about these two people, that's for HR, legal and senior management to deal with, and they have the tools and processes to actual investigate. (Check your employee handbook, companies I have worked for in the past require employees to cooperate with HR investigations and refusing to comply can lead to termination). If there really wasn't any problem then HR will take no action (they don't want to get sued for wrongly terminating a manager either).