Word for a police man getting money from someone forcefully

My wife bought a puppet from a roadside salesman. She noticed a policeman taking away the money from the salesman forcefully.

Is there an appropriate word for the policeman's behaviour? Bribe is not the word because the salesman was not trying to bribe here. Words like rob, steal, loot come to my mind. But I want to know if there is a better fit.

Update: The way the incident was perceived by my wife (and the original intention in my question) is that the policeman did this for his personal gain and was not doing it as a part of his duty.

The appropriate word to use in this context (abuse of authority) is extortion.

Strictly applied confiscate refers specifically to appropriation for the public treasury (fisc).

Previously-suggested extortion (“The practice of extorting money or other property by the use of force or threats”) is quite appropriate; also consider verb shake down (“To get money from someone using threats”).

Edit: As noted in a comment, as a noun shakedown means “an act or instance of shaking someone down; especially : extortion”. Some other terms related to a policeman forcibly taking money from a salesman might include:
• graft, “Illicit profit by corrupt means, especially in public life”, “A cut of the take”, “A bribe, especially on an ongoing basis”
• squeeze (mentioned earlier by Daniël), “To oppress with hardships, burdens, or taxes; to harass”
• put the arm on, “Fig. to apply pressure to someone. [eg] John has been putting the arm on Bill to get him to cooperate.”
• muscling in, “[using] power or influence, esp. when based on force or threats of force”
• on the take, “trying to profit in a personal and usually financial way from a situation”, which might apply if the policeman knows of infractions but is turning a blind eye for a split of the stand's profits.

Note, cambridge.org has thesaurus pages for specific topics, including Cheating & tricking which may be relevant.