(CNN) -- The man who authorities accused of assaulting the 2-year-old son of NFL player Adrian Peterson now faces a murder charge.
State prosecutors released a grand jury indictment Monday that charges Joseph Robert Patterson with second-degree murder.
The new charge comes more than a week after the death of the Minnesota Vikings running back's son, who was living with his mother in South Dakota.
Patterson, the 27-year-old boyfriend of the toddler's mother, is accused of recklessly causing "serious bodily injury to the child," according to the indictment. He also faces charges of first-degree manslaughter, aggravated battery of an infant and abuse or cruelty to a minor.
Authorities have said that the child suffered injuries to his head consistent with abuse.
"Patterson will be booked under the new charges and will be arraigned in the near future," the Lincoln County Office of the state's attorney said in a statement Monday.
Peterson returned to the field last week.
In a text to a Fox Sports reporter, Peterson said he decided to play again for the same reason he participated in the NFL's skills testing event for potential draft picks a day after his brother died in 2007.
"God wants good to come from it," he told "NFL on FOX" sideline reporter Laura Okmin in a text before the game Sunday.
He tweeted thanks to fellow players, some of whom had taken to the social network to defend his decision to play.
"The NFL is a fraternity of brothers and I am thankful for the tweets, phone calls and text messages from my fellow players," he tweeted after his son's death.
After the game last Sunday, Peterson's teammate, tight end Kyle Rudolph, praised Peterson's determination and heart.
"I can't imagine, you know, the heavy heart that he had today, being out on the field," Rudolph said. "But he spoke to us right before the game, right before he took the field and said he was going to give it his all, for all four quarters, and that's exactly what he did."
"He said, 'I'm going to give it my all, and I expect you guys to do the same,'" Rudolph said. "For a guy like that, how can you not?"