Step 1
The House of Representatives holds a few hearings, then they vote to impeach the President. If the House of Representatives votes in favor, by a majority, the House sends Articles of Impeachment to the Senate.
Step 2
The Senate starts a trial of the President to decide if the President is guilty of the crimes charge in the Articles of Impeachment. If 2/3 of the Senate votes to accept any Article of Impeachment, the President is automatically removed from office and the vice president takes his place as the new president.
*So far, no president has been impeached.
In order to answer this question, I will use two different perspectives of ethics: the consequentialist perspective, and the deontological perspective.
Consequentialism argues that the morality of an action lies with its consequences. This means that an action with bad consequences is an immoral action, and vice versa. In this case, killing the last remaining Redwood would not have any negative consequence on any being in the world, as no one benefits from it anymore. This means that the act is not immoral.
A deontological perspective states that there are principles that should be taken as rules, and which govern what is right and what is wrong. Therefore, rules and duties are central. For example, a principle might state that "all life is valuable." As the Redwood falls under the definition of life, killing it would be considered an immoral action.
The Battle of Antietam was considered a turning point in the Civil War because this was the first major Union victory in the East.