Upsetting incident with colleague

[SalsaGemini]

Good afternoon MN

Hoping I can get some help here.
I for a great organization & in a large team that offers counselling, advice & support to families.
I have a number of great colleagues & I love my job.
Or I did.

One colleague is notoriously difficult to manage (she is now managed by me (other manager left) & another person manages her too due to working some different days etc) - she has a different job to me, & there have been issues with performance, competence & general attitude over the last year which have been addressed. Things seemed ok/better for a while, then a few issues were discussed last week with this colleague, her other manager & myself in a meeting, this was all online.

The colleague arrived at the meeting & was clearly already on edge.
Within 5 minutes she had been extremely unpleasant & rude to me, and her other manager, especially rude to the other manager, accusing them of being unsupportive, of lying to her & some other stuff that was completely untrue/inappropriate. She was very heightened & refusing to listen to either of us, we ended the meeting, & I spoke to my manager advising her of the incident, who so far has not responded.
Next week I am off all of next week, the other manager has messaged me saying they don't want to have to speak to this colleague & believes that their mental health has been impacted by this horrible outburst.

They are also concerned that the colleague is not coping, both at home & at work.
I was really shocked by what happened & am aware the other manager is being encouraged (by their partner) to file a grievance against the colleague & wants me to speak to HR as well & do the same.

I feel like this is necessary as the colleague was completely out of order but worrying about what might happen to the colleague, & also whether HR will actually do anything, so is it worth it.
We are so very busy at work & I don't want to have this extra issue but I think the colleague will do this again & next time could be even worse. The language & attitude of the colleague goes against what is permitted in terms of the organization's policies around communication with others at work.

Any advice/thoughts are welcome.
It all feels awful & utterly uncomfortable & I have never experienced anything similar before.

@SalsaGemini being honest this is going to be time consuming but you need to support your colleague. I suggest you and your colleague start by writing down what happened in the meeting and then speak to HR and your line manager(s). Stress it was a breach of policy but also the impact on you both.

It may lead to a grievance or it maybe that HR talks to her to try and get to the root of this. As you state she has a reputation for this HR may advise a different route e.g. disciplinary or performance improvement plan.

Thanks @Harassedevictee
You're absolutely right, & I think with both the other manager & myself together letting HR know the score, HR will hopefully be able to address things.
I've never had this in any workplace, this is the least toxic workplace I've ever worked in, hence feeling so shocked by it all.

If you are both her managers surely you should be going down the disciplinary route. I thought grievances only worked for people at the same lot above you in the hierarchy

I would first ask yourself why the person you’re managing may have reacted like this. You said there were some issues which they dealt with adequately and then from what you said they were called in to another meeting to face both of you with what sounds like more criticism? Was this the best way to deal with it? You said they arrived at the meeting on edge. Could they be feeling harassed by you both, did you both need to be there to address this with them? Did you give them an opportunity to explain why something had gone wrong, did you listen and consider what they were saying appropriately and respectfully?

I think anyone going in to a meeting to face two managers and more criticism would be on edge.

You have a responsibility for both colleagues, not just the other manager. Have you reached out to both to see if they are ok?

It sounds from your reaction that their response was out of the blue, so not the norm for them, so why is that?

I’m not saying their reaction was right but if you didn’t deal with this appropriately you could have left yourself open to having a grievance raised against you.

You need to write a grievance but as a kind word of advice, make it much clearer and concise than your post here.