The opinions expressed seemed to indicate that an indictment was required in order to make an arrest, which isn't factual.
BBM
I agree that an indictment is sought in order to bring a case to trial. I disagree that it's unusual for an arrest to be made prior to an indictment.
indictment n. a charge of a felony (serious crime) voted by a grand jury based upon a proposed charge, witnesses' testimony and other evidence presented by the public prosecutor (District Attorney). To bring an indictment the grand jury will not find guilt, but only the probability that a crime was committed, that the accused person did it, and that he/she should be tried.
http://legal-dictionary.thefreedictionary.com/indictment
If probable cause exists, an arrest can be made prior to an indictment. This entire discussion began due to the question being posed as to whether or not an indictment is necessary in order to make an arrest.
Justification for Arrest
The Fourth Amendment requires courts to confirm that an arrest is supported by probable cause either before or shortly after officers take a suspect into custody. A judge or magistrates signing an arrest warrant serves this purpose, but most arrests dont involve warrants. As a result, officers have to get quick probable cause determinations in order to hold most arrestees in jail. But states dont have to afford defendants an actual hearingrather, it suffices for the prosecution or arresting agency to provide a prompt written statement that a judge or magistrate endorses. (See, for example, D.C. Super. Ct. R. Crim. P. 5(c).)
http://www.nolo.com/legal-encyclopedia/what-probable-cause-hearing.html
I misspoke when I stated that folks said it never happens - I apologize.
The fact of the matter is that arrests of both police officers and private citizens have occurred prior to an indictment, because an indictment isn't necessary to make an arrest - probable cause is the deciding factor regarding an arrest.
An indictment pertains to whether or not a prosecutor can or will bring a case to trial.