You've made the wrong hiring decision... now what?
If you're a people manager, you've probably been in this position before where you hired someone who you thought would be an excellent fit with your team. On paper they looked great! In-person, they were fantastic during the interview and answered all your behavioural questions perfectly! What could have happened!??!
Well it's too late to start diagnosing what went wrong and how you could have been so off on your assessment about this person. Your immediate concern is to handle the problem at hand first as you've been hearing some rumblings from your normally friendly and welcoming team. Or maybe someone from your team just came straight out and told you that there's something off with your new hire because they did this, reacted like this, etc.
A bad employee can be toxic to a work environment. The thought being from your existing employees "if so and so doesn't care and the manager is letting them exist, why should I care?". You need to get ahead of these situations sooner rather than later. The ability as a manager to have tough conversations at work (also a great skill to have in life) is so important. You'll be seen as a more effective leader overall.
One of the best executives I worked for before taught me this lesson. He was charismatic, incredibly sharp and intelligent, and knew how to motivate and get the best out of people. Even he was prone to a hiring mistake. A few years ago, his newest hire was having trouble meshing with the team and so feedback got back to him. He addressed his employees and set the expectation that everyone deserves a chance but told them he would be keeping an eye on the situation. He took ownership and organized subsequent weekly chats with the new hire and eventually after a month, he cut her loose. Although it reflected badly that he was the one who hired her in the first place, he got over his ego quickly. His reputation after he took ownership and handled the bad hire, gave him even more respect from his team around him. If he had let that person hang around longer or done nothing, the resentment from his existing team would have festered and eventually affected the morale.
We are all human and we make snap judgements, especially when interviewing someone in 30 min (maybe 45 min) and trying to assess how successful they'll be in a job. Our decisions are not always based on facts but rather assumptions we make due to our human nature. These leaves us open to making errors when judging people for jobs, even if you're one of the smartest execs that I ever worked with. But how you react, take ownership and resolve the situation, is almost as important in making the right hiring decisions.