The new boss, Jonathan, fired Tom; Tom feels as if it was an injustice firing and feels wronged.
At first, Tom lost everything, when he lost his jobs entire life went downhill and its all collected to this point where after months of pent-up rage against Johnathan he finally loses it completely; and decides to kill Johnathan.
He waited till the office Christmas party because it would be easy to sneak into the office as Santa.
He waited until the perfect moment to strike, but what he didn't know is it wasn't the perfect moment someone saw and they had already called the police.
He did not successfully kill Johnathan and he will also be on trial for attempted murder and is unlikely to get off not guilty.
Sadly for him, his plan ended in him being granted 25 years in prison and a restraining order from Jonathan.