How do I say no for lunch or coffee to this guy at work?

I work with this guy who is 23.

He was ok at first but the last few months, he's been a bit weird.

Our backs are towards eachother and sometimes he would just turn around and stare at me for ages which made me uncomfortable. He also stares longer than usual when he talks to me also.

It's only been these last few months he's been doing this.

It creeps me out. He asked me for lunch before I went away overseas. I had to make up a lie to get out of it.

He is leaving for good in 2 weeks & he wants to have lunch before he goes.

We have lunch break at the same time but not with eachother.

How do I get out of it? He knows I'm not having lunch with other work mates every day so I'm not sure what to say.

His dad also works in the office so I don't want the dad to think I'm ignoring him.

Not sure how to say no to him.

I also want to delete him from my IG but not sure he would tell I did. His dad is also leaving in March for retirement.

How do I say no for lunch or coffee to this guy at work?
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