PORTLAND – Prosecutors will not pursue murder charges against one of two brothers charged in the fatal stabbing of a Portland teenager last fall.

Antwane Mills, 18, pleaded guilty Wednesday in Cumberland County Superior Court to burglary and assault and faces three years in prison with all but 18 months suspended. In exchange, the state will drop murder and felony murder charges against him.

Brandon Mills, 20, still faces a murder charge in the stabbing death of 16-year-old Jarmaine Ramirez in his family’s second-floor apartment in Portland. Prosecutors say the Mills brothers stormed up the stairs to the apartment after two girls threw water on Antwane Mills and other passers-by on Congress Street on Oct. 21.

Several witnesses saw Antwane Mills struggle with Ramirez’s sister, and one witness said he saw Brandon Mills stab Ramirez. But there is no evidence that Antwane assisted his brother, said Assistant Attorney General Lisa Marchese.

“There is no question that Antwane set in motion the events which led to Jarmaine’s death,” Marchese said. “But I don’t have the evidence to prove that he went there to kill or that he knew that his brother was going to do it. Logical inference would tell you that he did. But knowing and proving are two different things.”

The deal with Antwane Mills will not be final until Brandon Mills’ case is resolved, Marchese said. Brandon Mills has pleaded innocent.

While the agreement does not require Antwane Mills to testify against his brother, he answered several questions under oath Wednesday that could limit his ability to help his brother’s defense.

Mills was asked whether he stabbed Ramirez, whether he saw who stabbed Ramirez, whether he knew whether his brother was armed with a knife, and whether he saw Ramirez or anyone else with a knife. He answered no to each question.