A grand jury has elevated charges to first-degree murder against a 22-year-old man accused of shooting his older brother and their father, an Elk River police officer.

If Christopher Besser is convicted on that charge, it means the most serious of sentences possible in Minnesota: life in prison without parole.

The grand jury Tuesday returned its indictment on two counts of first-degree premeditated murder in the shooting death on May 9 of Besser's father, 49-year-old Todd Besser, and brother, Blake Besser, 27, at the St. Michael, Minn., home where the two sons were living. The indictment also includes charges of second-degree intentional murder.

Christopher Besser made his first appearance Wednesday on the indictment, which County Attorney Tom Kelly had said all along he would be seeking. The defendant remains jailed in lieu of $2 million bail with conditions.

In the initial charges, prosecutors alleged that Christopher Besser was angry with his father's expectations of him and said he "just lost it" and carried out the killings with a hunting rifle kept in the home where Todd Besser once lived and visited at times.

Moments after shooting his father in the back of the head, Christopher Besser allegedly killed his brother in the kitchen with the same weapon and walked out as the gravely wounded older sibling was on the phone with police.

Christopher Besser was arrested at a convenience store in nearby Monticello, less than an hour after his father and brother were shot in the home in the 4500 block of Mayfield Avenue.

While at the store, he called 911 and explained what he did, according to the criminal complaint. He added that he shot his brother because he didn't want to leave a witness to their father's death, according to the charges.