AITA For getting my coworker fired after he tried blaming me for his screwup

This happened a few years ago when I was 22 and working at a warehouse. Mostly receiving shipments, checking inventory and scanning stuff. Boring job, but it paid decent.

I’ll call the guy Mason. He was probably 30 or 31 and had been there about 4 years before me. At first he was actually really helpful and we got along pretty well.
Then Mason figured out that if work needed done, I’d probably just do it.

Somehow he was “backed up” every day. Bathroom breaks, phone calls, sitting outside. Then he’d come back at 3:30 acting exhausted.

“Man today has been crazy.”

Crazy for who, dude? I just watched you spend 15 minutes showing somebody a bass boat on Marketplace.

One Saturday it was my sisters’ birthday. I told Mason I had to leave on time for her birthday dinner.

Around 2 PM he disappeared for almost an hour. I eventually found him sitting in his truck on his phone.
At the end of the day he asked me to finish his work. I said no.

Monday my supervisor pulled me aside because Mason said I left with unfinished work. I got the classic “you guys need to communicate better.”

After that Mason started blaming mistakes on me and suggesting I do every shitty task.

Then something worth around $1,200 went missing. The system showed Mason received it, and he immediately said he handed it to me.

He did not.

I got pulled into the office because “Mason is pretty sure he gave it to you.”

That was when I actually got worried. My family barely had money as it was, so once I started working full time I tried to handle pretty much everything myself. I knew my parents would help if I lost my job. I just didn’t want it to come to that.

I had maybe $400 saved, bills coming up, and an old Buick that constantly needed something fixed. Mason knew all of that too. So him trying to dump this on me pissed me off way more than his usual lazy bullshit.

About an hour later they found the item. Mason put it on the wrong rack and never scanned the new location.
Nothing happened.

Supervisor just told “us” to be more careful.

What the hell did I do? Exist nearby?

After that I stopped covering for him. If he disappeared, I didn’t make excuses.

Then the revenge happened almost by accident. Mason was always reselling phones, tools and whatever else he could flip. One day he showed a coworker a drill and said, “I got this one through work.”

A few days later I saw him put something in his backpack. Then I saw him do it again, except this time I knew it belonged to the company.

I told our supervisor, “you might want to check the cameras around 3:30 yesterday.”

The next day Mason got called into the office. About 45 minutes later he walked out with his backpack and never came back.

Apparently they checked older footage and found he’d been taking stuff for months and selling it. A cop came in later. No idea if he ever got charged.

I felt a little weird about it afterward because he had a kid and had helped me when I first started.

AITA?