TL;DR
Co-worker doesn't do his job and is trying to blame me for his low performance, what is the best way to get out of this situation? Is talking to his manager a good option?
At my company, my boss asked me to do some side work on another team because they didn't have enough people at the time (only one person was left), this situation wouldn't go on forever, but it has been going on for some time. The work I do on the second team isn't too bad, just annoying, but the person who was left on this team was just terrible.
First of all, this person has a company of his own (more like, he owns an eBay account that sells some products) and he spends a lot of his working hours inside our office handling problems that his own company comes up with. He's constantly going out to pick up personal calls, and recently he gave his company extension to his own clients, who have started calling him on the company's phone. He also spends a lot of time (around two hours) just hanging around the office using his cell phone, probably taking care of his personal business.
None of that should matter to me, except that at the beginning of my "helping", he gave me a lot of tickets to work on saying it was necessary for me to get some experience. If I asked him how to do something, he'd say "I'll let you work on that for a while" and proceed to take care of his company. He would then forget he asked me to do anything and only show up to ask me how it was going when a superior asked him how it was going. Many times some solution he had wouldn't work and I had to ask other people how to solve it. I wouldn't mind doing this at all, because I'm learning after all, but all the time (I found out later) he wasn't working on anything our company needed, he tricked me into thinking he was doing essential office work that kept him very busy, while in reality he was managing his own company from his cell phone.
When I realized that I got really mad, but I didn't want to do anything because I didn't want to create a toxic environment by complaining to him or to his manager. Instead, I've tried as hard as I could to stay only on my own team (whose work I did there started getting slower because of all the demands this person was throwing on my back) and kept swallowing this person's actions all the time. Then, when he started sending me messages when I had already left the office to ask for something his manager asked him how was going, I couldn't take it anymore. When I informed him I still had not done it, he started being ironic when I asked him to teach me how to do it, ending up with him completing the task. I then started focusing more on my own team instead of doing his job for him and that seemed to get him annoyed, but he never complained to me or demanded I did more work on his team. Instead, another employee told me that this person was asking my manager if I was relieved from this person's team, because I wasn't doing anything to help him anymore and that he was going to file up a complaint about me to his own manager.
The thing is, I was informed I was going to leave his team (since they hired two other people to help him), so I just focused more on my own work instead of his demands. My manager and coworkers were aware of this and stood up for me, but he said he was filing a complaint and we never found out if that was true or not. His own manager seems to be aware of this guy's behavior and terrible work habits, but he only complains and fight him without ever solving the problem properly. To make matters worse, he's now on vacation and this guy has started getting even more annoying and explicit about managing his business and spending free time during work hours. Another employee noticed he was taking pictures of his teammate's notebook when he thought no one was looking, as if he was trying to get evidence for something. He also called a woman once and pretended to be a cop (a crime in my country) to get her scared because she owed him money (I listened to the whole conversation as it happened beside me), while collecting her data (such as SS number) from a company he used to work on (and who didn't remove his access).
Is there any way I can let people know what he's doing, specially his manager? It doesn't seem ethical nor appropriate to behave this way and still try to shift the blame to other people... my major concern is that people will listen to his complaints about me and not look into his behavior, making things end up badly for me because of that. The only ones who know about what he's doing are those who sit around him and those who worked on his team previously, I never complained about him to my manager or his, so I'm not sure if there's a formalization about how displeased I was.
This is my first job, so I'm afraid to handle it improperly and on a non-professional basis, as I feel I've already done it.