In Minnesota, an offense carrying a penalty of life imprisonment, such as first-degree murder, may only be brought by a grand jury indictment. That’s coming.

With 57-year-old Vance Luther Boelter having been apprehended on Sunday in connection with the murders of Minnesota state Representative Melissa Hortman and her husband, Mark Hortman, as well as the apparent attempted murders of state Senator John Hoffman and his wife, Yvette Hoffman, the question arises as to why he has thus far been charged with second-degree murder, not first-degree murder.

The simple answer is: There is a Minnesota criminal procedure statute, Rule 17.01, which requires a grand jury indictment in any case in which the offense charged is punishable by life imprisonment. Minnesota does not have the death penalty. Murder in the first degree is punishable by mandatory life-imprisonment (the statute is here); murder in the second degree is punishable by up to 40 years’ imprisonment (the statute is here).

The main difference between the two degrees of murder is premeditation. First-degree murder requires proof beyond a reasonable doubt that the murderer acted with premeditation — i.e., he targeted the victim ahead of time and carried out a plan to kill the victim. Second-degree murder requires proof of intent (i.e., the killing has to have been done on purpose, not by accident) but not of premeditation.

Then there are the practical considerations. Boelter was arrested after a manhunt over the weekend. There has not yet been time to do a full investigation, much less for prosecutors to present the case to the grand jury and seek an indictment. Generally, at the preliminary arrest stage after a violent crime, a person is charged in a criminal complaint, which lays out probable cause to charge him with a crime serious enough to warrant detention pending indictment and trial. At this point, a second-degree murder charge fulfills that purpose.

Plus, prosecutors always want to move from the less serious to the more serious charges as they proceed from arrest to indictment; going from more serious to less serious would signal that the investigation has turned up unanticipated problems with the case.

So when he appears in court today, Boelter will stand charged with second-degree murder. I expect within a couple of weeks, he will be indicted on charges of first-degree murder, attempted murders, and more.

There is some talk of potential federal charges. For now, though, the Trump Justice Department and the FBI should simply offer whatever investigatory and forensic help they can to Minnesota’s police and prosecutors. This is a state case, involving the most serious of state crimes against state officials. The state prosecution should take precedence.

As I’ve noted in other contexts, murder is mainly a state offense. There are federal murder statutes that apply when a killing triggers some federal interest (e.g., murder of a federal official or foreign diplomat, murder committed by an interstate or international criminal enterprise, murder through terrorist attacks, or murder through use of facilities in interstate commerce). In this case, however, the state interest is patent and there is no obvious federal interest. Hence, the state should proceed with its prosecution and the feds should provide whatever help they can while doing their own analysis of whether federal charges are warranted.